Mix the egg, sugar and oil with the mixer until frothy. Then sieve the flour and baking powder, add the salt. Stir everything into the egg-sugar-oil mixture. The dough shouldn`t be too runny. Finally stir in the mineral water.
Butter or oil 3 small porcelain molds or cups. Divide the batter into the molds and put a cube of chocolate in the middle. Fill the containers only half full with batter. Bake the cakes without a cover for 2 minutes at 450 watts, then for 1 minute at 720 watts.
Serve the cakes with cream if necessary.
Tip:
The weight of the egg (65 grams) gives the amount of sugar and flour.