The calculation is for a 18-20cm (7.10-7.90 inch) baking tin.
- Whip the eggs with sugar until fluffy white mass (10 minutes with a hand mixer).
- Sift the flour, cocoa and baking powder in two stages, mix gently with a spatula.
- Add boiling water and vegetable oil, and stir.
- Bake the sponge at 338F (170C) for 30 minutes. Check for readiness with a skewer.
Combine the components in a saucepan, and boil until sugar dissolves. Cool.
- Cut the sponge into 3 cake layers.
- Soak each sponge, and grease with Nutella.
- Lay out slices of chopped strawberries.