Preheat oven to 180 °C/350°F.

Place cream in a saucepan and bring to the boil. Reduce heat, stir in the chocolate and when it has just melted, remove from heat and stir in bicarb of soda. Allow to cool.

Place eggs in a large bowl. Add sugar and, using an electric beat, beat until the mixture forms a tick ribbon. This takes about 10 minutes. To incorporate most of the air, make large movements with the beater.

Gently beat in the melted chocolate until just mixed in.

Add sifted flour all at once and, using a rubber spatula, fold in gently but quickly. When you see the last of the flour has disappeared, incorporate the melted butter gently but quickly.

Pour mixture into prepared tin and smooth top with spatula. Bake in preheated oven for 30 - 40 minutes.

When the sponge is cooked, remove it from the oven and leave to cool for a few minutes before gently unmoulding onto a wire rack.

Per serving: 1958 Calories (kcal); 167g Total Fat; (74% calories from fat); 52g Protein; 80g Carbohydrate; 1767mg Cholesterol; 1304mg Sodium Food Exchanges: 0 Grain(Starch); 6 1/2 Lean Meat; 0 Vegetable; 0 Fruit; 30 Fat; 5 Other Carbohydrates