First, beat the egg whites with salt and sugar until soft peaks form. Do not overbeat to avoid breaking the layers after baking.
Sift the flour and add it to the egg whites, gently folding with a silicone spatula. Gradually add the walnuts and mix lightly to maintain the airy structure.
Divide the mixture into 4 equal parts. Prepare a 24 cm diameter baking pan lined with parchment paper and lightly greased. Bake each layer separately at 180°C for about 10 minutes.
For the cream, you can alternatively use 200 g milk chocolate and 200 g dark chocolate melted in 400 ml cream. If you prefer a chocolate mousse, whisk the yolks and sugar over simmering water until fluffy.
Melt the butter and add cocoa. Combine this mixture with the cream and whisk again over the water bath. Add the cream and mix until smooth and thick.
Assemble the cake by alternating layers and cream, finishing with a layer. Let the cake rest in the fridge overnight.
The next day, prepare the glaze by melting the chocolate with milk or cream. Pour over the cake and decorate the edges with crushed walnuts or coconut flakes.