Sift together the flour and the cocoa powder. Beat the eggs with the sugar and salt until they resemble like thick shaving foam. Fold the flour mixture into the egg mixture with gentle motions (guys, fold and not stir! Stirring will cause the mixture to deflate). Transfer the mixture into the pan and bake the cake for 45-50 minutes or until a tester comes out clean. Let it cool, level and cut into 3 layers. Refrigerate it for 1-2 hours or overnight, for easier cutting.
What you need to do for the mold:
Cut 2 discs of baking paper the same size as your pan and place them both at the bottom of the pan (the 2 baking paper discs help with easier unmolding when the cake is cold).
Cut 1 strip of acetate 4 1/2 inches (11 cm) high and 28 inches (70 cm) long. If your acetate is shorter you can cut 2 strips. Place it in the pan to make a mold with tall edges and secure it with some scotch tape or clips. Now you have a mold tall enough to fit your cake!!!
(If you can’t find acetate you can use strips of a sturdy paper along with strips of baking paper. Just line the sturdy paper inside the pan and repeat with the baking paper. Secure them with some clips. This way, the cake touches only the baking paper)
***If you don't want to use the acetate strips method, you can use a 10-inch springform baking pan. This will result in a wider and shorter cake. You will cut the sponge cake into two layers and divide the mouse into two layers also.
Add the meringues just before cutting the cake, to keep them extra crispy.
Keep refrigerated for up to 3-4 days.
This cake is best eaten slightly chilled.