Preheat the oven to 180°C (350°F). Grease a bundt or ring-shaped cake pan and dust with flour.

Separate the eggs. Beat the egg whites with a pinch of salt until stiff peaks form.

In a separate bowl, whisk the yolks with sugar until pale and fluffy.

Sift in the flour and cornstarch and gently fold into the yolk mix.

Carefully fold in the egg whites. Pour the batter into the pan and bake for 35–40 minutes, or until a toothpick comes out clean. Let cool completely.

In a saucepan, whisk milk, sugar, cornstarch, and vanilla. Cook over medium heat, whisking constantly, until it thickens into a pudding. Remove from heat and let it cool to room temperature (cover with plastic wrap to prevent skin from forming).

Beat the soft butter until fluffy. Slowly add the cooled pudding, one spoonful at a time, beating constantly, until smooth and creamy.

In a dry pan, melt 100g sugar over medium heat until golden. Stir in the chopped hazelnuts or almonds, and mix quickly. Pour onto parchment paper and let it cool.

Once hardened, crush into small pieces using a rolling pin or food processor.

Carefully slice the cooled cake into three horizontal layers. Spread a thin layer of jam on the bottom layer, then add a layer of buttercream.

Place the second cake layer on top, repeat with jam and buttercream, then top with the third layer.

Cover the whole cake with a smooth layer of buttercream.

Press the crushed brittle evenly over the outside of the cake. If desired, pipe buttercream rosettes on top and place cherries or jam dots in the center of each rosette.

Chill the cake for 1–2 hours before serving.