Mousse: Soak the gelatin in cold water.
Put water in a saucepan, add sugar and let it boil for 3 minutes.
Whip the egg white.
Add the soaked, squeezed gelatin to the boiling sugar mixture and stir until dissolved. Pour in a fine stream into the whipped egg white and continue whipping until it is firm and cold.
Put the strawberries and lemon in the blender and mix until coulis, set aside 300 ml.
Gradually mix this into the mascarpone.
Fold in the whipped egg white.
Biscuit: Separate the eggs and whip the egg white stiff with the sugar. First mix in the yolks and then the sifted flour.
Put in a piping bag and pipe long lines on a baking sheet with parchment paper, leaving a narrow space of 1-2 mm between each line, sift powdered sugar over it.
Pipe a round circle of dough for the bottom of the baking pan (diameter 20 cm) and sift powdered sugar over this as well.
Bake for 5' in a preheated oven at 230Β°.
To check if it is baked enough, you can press down on the dough. If it leaves a dent, it is not baked enough; if the dough rises back up, then it is okay.
Let cool.
Tips
Degrease material well so that you can beat your protein very stiff!