Prepare the Yuzu Curd (Day One)

In a medium saucepan, whisk together yuzu juice, sugar, whole eggs, and egg yolks until smooth. Set over medium-low heat and cook, whisking constantly, until the mixture thickens enough to coat the back of a spoon and registers 170°F (76°C), about 8-10 minutes. Do not let it boil.

Remove from heat and strain through a fine-mesh sieve into a clean bowl, pressing to extract all curd. Add cold butter cubes one at a time, whisking until each is fully incorporated before adding the next. Stir in salt.

Press plastic wrap directly onto the surface to prevent a skin from forming. Refrigerate at least 4 hours or overnight until fully set.

Prepare the Black Sesame Caramel Brittle (Day One)

Line a baking sheet with a silicone mat or lightly greased parchment. In a small heavy saucepan, combine sugar, water, and corn syrup. Cook over medium-high heat without stirring, swirling the pan occasionally, until the mixture reaches a deep amber color (about 340°F/170°C), approximately 8-10 minutes.

Immediately remove from heat, stir in black sesame seeds, butter, and salt. Quickly pour onto the prepared sheet and spread thin with an offset spatula. Let cool completely until hard and brittle, about 30 minutes. Break into shards and store in an airtight container.

Prepare the Coconut and Black Sesame Dacquoise (Day One)

Preheat oven to 325°F (160°C). Line two half-sheet pans with parchment paper. Draw two 9x13-inch (23x33cm) rectangles on each parchment, then flip the paper over.

In a bowl, whisk together desiccated coconut, powdered sugar, black sesame powder, and cornstarch. Set aside.

In a stand mixer fitted with the whisk attachment, beat egg whites on medium speed until foamy. Gradually add granulated sugar while increasing speed to medium-high. Continue beating until stiff, glossy peaks form, about 4-5 minutes.

Gently fold the dry ingredients into the meringue in two additions, being careful not to deflate. Divide the mixture among the four rectangles, spreading evenly to about ½-inch (1cm) thickness using an offset spatula.

Bake for 20-25 minutes until the dacquoise is light golden, dry to the touch, and slightly crisp on the outside but still chewy within. Cool completely on the pans.

Prepare the Black Sesame Almond Joconde (Day Two)

Preheat oven to 425°F (220°C). Line two half-sheet pans with silicone mats or parchment paper.

Sift together almond flour, powdered sugar, black sesame powder, and all-purpose flour. Set aside.

In a stand mixer fitted with the whisk attachment, combine the dry ingredients and whole eggs. Beat on high speed for 5 minutes until pale, thick, and tripled in volume.

In a clean bowl with clean beaters, whip egg whites to soft peaks. Gradually add granulated sugar and continue whipping to firm, glossy peaks.

Gently fold about one-third of the meringue into the almond mixture to lighten it. Fold in the remaining meringue in two additions, then drizzle in the melted butter while folding. Stop as soon as the batter is uniform—do not overmix.

Divide the batter between the two prepared pans, spreading evenly to about ¼-inch (6mm) thickness. Bake for 7-9 minutes until the edges are just set and the center springs back when lightly touched. Do not overbake or the joconde will crack during assembly. Cool completely before carefully peeling off the mat.

Prepare the White Chocolate Coconut Meringue Buttercream (Day Two)

Place white chocolate in a heatproof bowl and melt over a double boiler or in 15-second microwave bursts, stirring between each. Set aside to cool to room temperature (about 85°F/29°C).

Combine egg whites and sugar in the bowl of a stand mixer. Set over a pot of simmering water and whisk constantly until the sugar dissolves and the mixture reaches 160°F (71°C).

Transfer to the stand mixer fitted with the whisk attachment. Whip on high speed until the meringue is thick, glossy, and cooled to room temperature, about 8-10 minutes.

Switch to the paddle attachment. With the mixer on medium speed, add butter one cube at a time, waiting until each is incorporated before adding the next. The mixture may look curdled at some point—keep mixing and it will come together into a silky buttercream.

Add the cooled melted white chocolate, coconut extract, toasted coconut, and salt. Mix until smooth and uniform.

Prepare the White Chocolate Ganache (Day Two)

In a small saucepan, heat heavy cream until it just begins to simmer.

Pour hot cream over chopped white chocolate in a heatproof bowl. Let sit for 1 minute, then stir from the center outward until completely smooth. Let cool to a spreadable consistency (about 75°F/24°C), approximately 30 minutes at room temperature.

Assemble the Slices

Trim all dacquoise and joconde layers to identical 9x13-inch (23x33cm) rectangles using a sharp knife and ruler.

Place one dacquoise layer on a parchment-lined sheet pan. Spread a thin layer (about ⅓ cup) of yuzu curd evenly over the top.

Top with one joconde layer. Spread a generous layer (about ½ cup) of coconut meringue buttercream over the joconde.

Place a second dacquoise layer on top. Spread another thin layer of yuzu curd.

Top with the second joconde layer. Spread remaining buttercream in an even layer.

Place the remaining dacquoise layers on top. Spread the white chocolate ganache over the top in a thin, even layer.

Refrigerate the assembled slice for at least 4 hours, preferably overnight, until completely firm.

Finish and Serve

Whip cold heavy cream with powdered sugar and vanilla to medium-stiff peaks. Transfer to a piping bag fitted with a star tip.

Using a hot, dry knife (dip in hot water and wipe clean between cuts), trim the edges of the assembled slice for clean sides. Cut into 12 even slices.

Pipe a rosette of Chantilly cream on each slice. Top each rosette with a shard of black sesame brittle. Serve immediately or refrigerate for up to 2 hours before serving.