Recipe/Tutorial: (Sailor Moon Dessert Series, Pt. 9) Michiru’s Lime and Sea Salt Opera Cake

I absolutely adore Michiru. She is a incredibly perfect example of grace and elegance. I mean, even WITHIN the universe, everybody’s jealous. None of us can be as classy as Michiru.

I really wanted to incorporate the Deep Aqua Mirror. In addition to being a lovely design, I included the Space Sword and Garnet Orb in the last two desserts, so it seemed only right. Having a Neptune symbol embedded in glaze was an idea I was immediately super excited about. I also knew right away that this dessert would contain sea salt. Salted desserts are delicious, for one, but come on… Neptune. Sea salt. It just makes sense.


Key Lime and White Chocolate Opera Cake with Sea Salt Macarons

Yield: 6-7 individual cakes.

Timing notes: It is best to allow yourself about two days of working time for this recipe. The macarons benefit from resting for 24 hours, and the cake will be far easier to work with if it has had a long time to chill.


White Chocolate Ganache, recipe follows
Key Lime Buttercream, recipe follows
Lime Joconde, recipe follows
Lime Glaze, recipe follows
Coconut Rum Syrup, recipe follows
Sea Salt Lime Macarons, recipe follows
16 oz (450g) White Chocolate
Sea Salt
Vegetable Oil


1. The process for filling this cake is identical to the one for Haruka’s cake, so a glance at her recipe may be helpful. To begin with, cut your joconde sheet in half to make two smaller sheet cakes. Carefully split each sheet of cake into two thin layers. Choose one layer and spread a very thin layer of white chocolate on top. Flip the chocolate side onto a piece of parchment and allow it to firm up. The purpose of this is simply to make moving the slices much easier later on.
2. Begin assembly. Brush a small amount of syrup onto your cake, and spread a level layer of lime buttercream on top. Top it with another cake layer, syrup, and then a layer of ganache. Top this with a cake layer, syrup, and buttercream. Finally, place on your final cake layer. Spread an extremely thin layer of buttercream on top of your cake to create a barrier that will prevent the glaze from seeping into the cake. Refrigerate. Once cool, use an oval pastry cutter in the size you want your cake to very gently stamp an oval pattern on the top of your cake. You should get 6-7 ovals. Be sure not to punch through the buttercream layer, or your glaze will seep into your cake and dye it blue. While your cake is chilled, use your white chocolate to pipe 6 neptune symbols on a sheet of parchment, plus a few extra in case of breakage. Allow to firm.
3. Gently warm your glaze. You don’t want is so hot that it will melt the buttercream. Using strips of stiff plastic (acetate), make a “barrier” around the edges of your cake so that the glaze won’t leak everywhere. Pour on a very thin layer of glaze. Wait until it begins to firm up partially before carefully placing your piped neptune symbols at the center of each oval. Press it down gingerly to make them sit level with the first glaze layer. Pour a second layer of glaze over the top, and then chill completely.

4. Using a clean, warmed knife, cut out the rectangular area around each oval. If you try to stamp out the ovals when the sheet is whole, you’re more likely to break it up. Use clean oval cutters to cut through the cake and make 6 oval mini cakes.
5. Have you tempered, melted white chocolate ready. As is often the case, a “faux” temper with a small amount of vegetable oil is acceptable. Wrap a sheet of plastic around each of your cake slices, and secure it with tape. Then wrap a SECOND layer of acetate around each layer. Finally, cut a piece of acetate long enough to wrap around your cake pieces with a little length to spare. Spread a portion of your melted white chocolate to coat this strip of plastic. While it’s warm, wrap your plastic around the double-covered cake piece. Allow it to firm before peeling out the outer layer of plastic. While the chocolate coat is still on the cake, use a warmed knife to cut a waved pattern as shown below.

6. Once your waved pattern is cut, carefully lift up the chocolate wrap. Detach the inner layer of plastic, remove the extra bits of chocolate and set aside. Repeat until you have 6 wraps. This way you can ensure they fit all of your cake pieces perfectly.
7. Place your cakes on the plate you intend to serve them on. Carefully lower the chocolate wrap onto your cake piece, and use additional melted chocolate to pipe dots along the edges.
8. Using your remaining chocolate, pipe abstract patterns on a sheet of plastic and sprinkle them lightly with sea salt. (I mean it, go easy! It’s very easy to oversalt.) Wrap the plastic around a rolling pin or paper towel tube while the chocolate is still warm, and adhere it with tape. Allow the chocolate to firm up in this position to create a wave garnish.

9. Place a macaron on top of each cake, and arrange some of your chocolate garnish around it. Experiment with placement to see what you like; this is a very flowy dessert and each piece of chocolate will be a bit different! Garnish the plate with extra glaze if you desire, then serve!


15 oz (400g) white chocolate
6 oz (170g) heavy cream

1. In a saucepan, heat the heavy cream to a simmer. Pour it over your white chocolate and allow to sit for five minutes before whisking together into a smooth mass. Chill in the fridge.

Key Lime Buttercream
12 oz (340g) butter
3 oz (85g) egg yolks
2 oz (60ml) water
8 oz (225g) sugar
1/2 cup (100g) sugar
4 tsp (20g) cornstarch
1 cup (240ml) key lime juice
Blue food coloring

1. In a saucepan, combine your sugar, lime juice and cornstarch. Be sure to thoroughly whisk everything so you don’t have any cornstarch clumps. Cook until it thickens, whisking vigorously the whole time. It will be VERY thick, so whisking is essential. Set aside. (This jelly mix looks crazy, I know, but it’ll work once it’s all done!)
2. Combine the sugar and water in a saucepan and begin to boil. Either keep a close eye on it or monitor it using a candy thermometer. If you don’t have a thermometer, check the sugar by dropping a bit into a cup of ice cold water. The sugar should harden into a pliable ball. In the meantime, beat the egg yolks until pale and doubled in size. When the sugar reaches 240°F (115°C), remove it from the heat. Allow it to cool for just a moment, and then very gradually pour the hot sugar into your egg yolks while beating vigorously. Once the egg yolk mixture has cooled down just a bit, but is still warm, add in the lime mixture and beat it until smooth. Beat the mixture until it has cooled to room temperature.
2. Once the mix has cooled, beat in the softened butter until you have a smooth, rich buttercream. Add blue coloring a drop at a time until you reach a pale teal color.

Lime Glaze
1/2 cup (120ml) water
1/2 cup (120ml) lime juice
2 tsp (7g) gelatin
6 tbsp (75g) sugar
Green and Blue food coloring

1. Sprinkle the gelatin over 1 tbsp of the water and allow to bloom for 5 minutes. In a saucepan, heat the lime juice, sugar, and remaining water until the sugar is dissolved and the mix has boiled for a minute.
2. Add in the bloomed gelatin, and stir until dissolved. Add food coloring a drop at a time until you achieve a sea green color.

Lime Joconde (adapted from Joe Pastry)
8 room-temperature egg whites
10 ounces (280g) almond flour
10 oz (280g) powdered sugar
7 large eggs
3.75 (110g) oz all-purpose flour
3 oz (85g) vegetable oil
Zest of 1 lime

1. Preheat your oven to 350°F (175°C) and line a medium sheet pan in parchment. In a large bowl, beat your egg whites to soft peaks. Add a couple tablespoons of the powdered sugar and beat until you reach medium to stiff peaks. Scrape the meringue into a different bowl, and use your first bowl to beat your whole eggs with the remaining sugar until light, fluffy and pale. Add in the almond flour and beat vigorously for an additional minute. Stir the lime zest into your flour, and then add the flour to your egg mix and stir until just combined.
2. Fold the meringue into your batter, taking care not to deflate it too much. Once it is mostly incorporated, fold in your oil. Spread the batter into your sheet pan and bake for approximately 15 minutes, or until a toothpick inserted into the center comes out clean.

Coconut Rum Syrup
4 oz. (115g) water
4 oz. (115g) sugar
Coconut Rum to taste (Start with 1 tbsp)

1. Combine the water and sugar in a saucepan and just bring to a boil before removing from heat. Stir in your rum.

4.3 oz (120g) almond flour
6.4 oz (180g) powdered sugar
3.5 oz (100g) egg whites
1 oz (30g) granulated sugar
Sea Salt

1. Preheat your oven to 300°F (150°C). Start by placing a large round tip (I use Ateco 806) into your piping bag and lining 2-3 cookie sheets in parchment (you may also use a silicone mat, but I have had much better results with parchment). If you need a guide for cookie size, now is the time to draw it on the underside of the parchment. Stand a piping bag in a tall glass with the edges rolled outward like a sleeve; this makes filling the bag much easier later. In a food processor, pulse together your almond flour and powdered sugar until well combined. In a separate bowl, beat egg whites until foamy. Gradually add the granulated sugar as you beat the whites. Once the whites have formed a stiff, glossy meringue, they are ready to go.
2. Sift about a third of your almond flour mixture onto the egg whites, and carefully fold them together until just incorporated. Sift on the remaining flour and fold it until just incorporated. Now you need to fold to get the batter to the correct stage. Fold slowly and rotate your bowl often. You want your batter to be thick and lava-like. I typically judge the batter by how long it takes for the fold mark to disappear. If the batter does not begin to smooth out, it’s not beaten enough. If it takes about 10 seconds for things to look smoother, you’re on the right track. Remember it’s much better to undermix than overmix macarons, especially since piping them continues to liquify the batter a bit.
3. Fill the batter into your piping bag. Pipe your macarons to about 1″ in diameter, at least 1″ apart. Once you’ve piped your rounds, sharply tap the cookie sheet on your counter to get rid of air bubbles. If you see any bubbles the tapping didn’t take care of, pop them with a toothpick. If your macarons have pointed tops, dip your finger in a bit of water and gently pat it down. Allow your macarons to rest for 20-60 minutes, or until the tops are no longer tacky. This may take longer if your kitchen is humid.
4. Bake your macarons for 15-20 minutes or until very slightly browned on the bottom. You should be able to carefully pull one of the macarons off of the sheet without the bottom sticking. Since the side ones are usually the ones that go wonky (see above), feel free to sacrifice one of the ugly ones to test if the macarons are done. Allow the macarons to cool completely. Once cooled, sandwich your macarons together with a bit of your lime buttercream. Brush a very thin layer of coconut rum syrup onto your macaron shells and sprinkle a tiny amount of sea salt on them. (I sprinkled a bit more on this macaron so it’d show up well in photos, but always opt for less salt than more.) Store the macarons, already filled, in the fridge or freezer. NOTE: Making and filling these a day ahead of time will actually improve their texture significantly.

This cake was light and delicious. I’m a huge fan of lime, so it was right up my alley! Be sure to go easy on the sea salt and this is sure to be a hit.


Note to my e-mail subscribers: Thanks to my butterfingers, some of you got a notification for an entry that’s not going to be done until next week. Sorry about that! It will be up next Monday.


  1. julie says:

    I absolutely love this idea! the fact that you’re a working pastry chef explains the level of plating and detail. great job!

Leave a Reply