Line a 6-inch baking pan with parchment paper. Do not grease the sides.
In a large bowl, beat eggs with sugar and salt using a hand mixer until the mixture triples in volume or reaches the ribbon stage. It should form a figure 8 with the egg mixture in the bowl.
Sift together flour and cornstarch in a separate bowl.
Gently fold the flour mixture into the egg mixture. Be careful not to knock the air out of the egg mixture.
Add 2 tbsp of batter to the melted butter. This will lighten the consistency of the butter.
Add the butter mixture into the batter and fold gently.
Transfer into the baking pan and bake in a preheated oven at 175°C for 25-30 minutes or until a toothpick comes out clean.
Allow the cake to cool completely before cutting.
Grind the berries in a grinder. Add powdered sugar and mix.
Whip the cold whipping cream in a cold bowl. Once it thickens, add powdered sugar and whip until soft peaks form.
Assemble the cake as desired. Decorate the cake with fresh berries.