Let's start cooking!
Place the grill at the bottom of the oven and preheat at 170 °C (325°F).
In a large bowl, mix the flour with half the sugar and salt. Set aside.
In another bowl, beat the egg whites with the electric mixer until they form soft peaks. Add the rest of the sugar and beat to firm peaks.
Slowly sprinkle half of the flour mix on the egg whites, and stir gently with a silicone spatula.
Slowly add the rest of the flour and mix until smooth and consistent.
Pour the mixture into the mould and bake for 40 minutes, or until the top of the cake is firm when touched with the back of a spoon. Put the mould on a grill and leave to cool completely before taking the cake out of the mould.
Preparation of the icing: mix the icing sugar and water in a bowl and pour on the cake just before serving, then sprinkle some Belgian Chocolate Thins cut into small pieces on top.