Preheat your oven to 300°F (150°C) and line two baking sheets with parchment paper, drawing three 6-inch circles on each sheet as guides.

In a clean, dry bowl, whisk the room-temperature egg whites until foamy. Gradually add the granulated sugar, one tablespoon at a time, whipping until you reach glossy, stiff peaks.

In a separate bowl, sift together the powdered sugar, almond flour, cornstarch, and salt.

Add about a third of the dry mixture to the meringue and fold gently with a spatula. Fold in the rest in two additions until just combined. If using toasted sliced almonds, fold them in gently now.

Transfer the batter to a piping bag or two spoons and form even rounds onto the prepared parchment within the traced circles. Smooth the tops lightly with a wet fingertip if needed.

Bake the rounds for about 25–30 minutes, turning the pans once midway, until they’re pale golden and firm to the touch.

Let the rounds cool on the pans for 10 minutes, then transfer to a wire rack to cool fully.

Chill a mixing bowl and whisk, then pour in the heavy cream, add the 1/2 cup powdered sugar and vanilla extract. Whip until soft to medium peaks.

Place one dacquoise round on a serving plate, spread a generous layer of whipped cream, add another round, more cream, and finish with a top round.

Dust with the extra powdered sugar and sprinkle the remaining sliced almonds.

Chill the assembled cake in the fridge for 20–30 minutes before serving.