Preheat your oven to 325°F (165°C) and line the bottom of an 8-inch or 9-inch springform pan with parchment paper. Lightly grease the sides of the pan with butter or non-stick spray to prevent sticking.

In a clean glass or metal bowl, beat the egg whites on medium-high speed until stiff peaks form, about 3-4 minutes. The peaks should stand straight up when the beaters are lifted.

Gently fold the powdered sugar, almond flour, and baking powder into the beaten egg whites using a rubber spatula. Fold carefully until just combined, making sure not to deflate the airy egg whites.

Pour the almond batter into the prepared springform pan, smoothing the top into an even layer with your spatula. Bake for 30-35 minutes, or until the top is golden brown and feels firm to the touch. Let the cake cool completely in the pan on a wire rack.

While the cake cools, prepare the yellow cream topping. In a small heavy-bottomed saucepan, whisk together the egg yolks, heavy cream, granulated sugar, and vanilla bean paste.

Cook the mixture over medium-low heat, stirring constantly with a whisk or wooden spoon, until the custard thickens enough to coat the back of a spoon (about 8-10 minutes). Do not let it boil, or the eggs will scramble.

Remove the custard from the heat and let it cool completely to room temperature. Once cooled, use an electric mixer to beat in the softened butter, 1 tablespoon at a time, until the frosting is completely smooth, thick, and fluffy.

Remove the cooled almond cake from the springform pan and place it on a serving platter. Spread the rich vanilla bean yellow cream evenly over the top, creating decorative swirls with an offset spatula. Garnish with toasted sliced almonds and a drizzle of melted dark chocolate, then chill for at least 1 hour before slicing to allow the cream to set perfectly.