• 225 g/ 8 oz dark chocolate
• digestive biscuits
• 60 g/ 2 oz butter
• 3 lemons
• 340 g/ 12 oz cream cheese
• 140 g/ 5 oz, plus 2 tbsp caster
• sugar
• 2 tbsp sultanas
• 3 eggs, separated
• 2 tbsp plain flour

Put the biscuits in a food processor with the butter and whiz to a crumb. Put this into a 23-cm / 9-inch non-stick cake tin and press down into an even layer.

Grate the zest from 2 lemons and reserve. Juice all three.

Preheat oven to 160°C/325°F/ gas 3.

Beat the cheese with an electric whisk until smooth, then beat in the 140 g/ 5 oz caster sugar. Continue to beat until fluffy. Fold in the sultanas. (If you happen to have some ready plumped up in brandy, all the better). Beat the egg yolks into the cheese, along with the flour, lemon zest and juice.

With a clean whisk, beat the egg whites until peaks start to form. Add the remaining 2 tablespoons of sugar and continue to whisk until stiff. Fold into the cheese and spoon over the biscuit base.

Stand the tin in a water bath and bake for 60 minutes, when the cheese should be set and golden. Remove, allow to cool and refrigerate for at least 4 hours or, better still, overnight.