Genoise

• 6 tablespoons chestnut flour
• ¼ cup cornstarch
• 6 tablespoons tapioca flour
• 2 teaspoons baking powder
• 1 tablespoon guar gum
• 8 large eggs
• 1 cup plus 2 tablespoons granulated sugar
• 2½ teaspoons pure vanilla extract
• 1 cup (2 sticks) unsalted butter, preferably cultured, melted

Buttercream

• ¾ cup granulated sugar
• 6 tablespoons water
• 4 large egg yolks
• 1½ teaspoons pure vanilla extract
• 1 cup (2 sticks) unsalted butter at room temperature

Glaçage

• 2 cups confectioners’ sugar, sifted
• 3 tablespoons water
• ¼ cup grade A dark amber maple syrup
• 1 teaspoon maple butter

For the genoise: Position an oven rack in the center of the oven. Preheat the oven to 350°F. Butter a jellyroll pan, line the pan with parchment paper, and butter the paper. In a small bowl, combine all the dry ingredients and stir with a small whisk to blend.

In a stand mixer fitted with the whisk attachment, beat the eggs until they begin to froth. Add the granulated sugar and vanilla and beat on high speed for about 5 minutes, or until the mixture is doubled in volume and forms a slowly dissolving ribbon on the surface when the whisk is lifted.

Fold the dry ingredients into the egg mixture, then stir in the butter just until blended.

Pour the batter into the prepared pan and smooth the top. Bake for 15 to 20 minutes, or until the cake pulls slightly away from the sides of the pan and is set and springy when touched. Remove from the oven and let cool completely in the pan on a wire rack.

Meanwhile, for the buttercream: In a small, heavy saucepan, combine the sugar and water. Bring to a boil over medium heat and cook until the temperature registers 239°F (soft-ball stage) on a candy thermometer.

Meanwhile, using a stand mixer fitted with the whisk attachment, beat the egg yolks until blended. When the sugar reaches the soft-ball stage, immediately pour it into the egg yolks and beat on high speed until thick and mousse-like. Beat in the vanilla just to combine.

In a separate bowl, whisk the butter until light and smooth. Gradually fold in to the cooled egg yolk mixture until smooth. Using a firm spatula, transfer the buttercream to a pastry bag fitted with a ⅝-inch plain tip and set aside.

For the glaçage: In a medium saucepan, combine the confectioners’ sugar, water, and maple syrup. Whisk until smooth. Turn the heat on low and whisk in the maple butter until smooth. Remove from the heat and pour into a glass bowl and let cool to the touch, stirring often to prevent a skin from forming.

Using a 3-inch heart-shaped cookie cutter, cut eight hearts from the genoise. Place the hearts on a wire rack set over a jellyroll pan. Carefully pipe the buttercream on four of the hearts and then top each heart with another layer of genoise. Flood the tops of each cake with glaçage until the entire cake has a uniform coating. Let stand for 30 minutes to set the glaze.