Step 1

Heat the oven to 180C/fan 160C/gas Crush the biscuits in a food processor (or put in a plastic bag and bash with a rolling pin). Mix with the butter. Press into a 20cm spring-form tin and bake for 5 minutes, then cool.

Step 2

Beat the cream cheese with the flour, sugar, a few drops of vanilla, eggs, the yolk and soured cream until light and fluffy. Stir in half the raspberries and pour into the tin. Bake for 40 minutes and then check, it should be set but slightly wobbly in the centre. Leave in the tin to cool.

Step 3

Keep a few raspberries for the top and put the rest in a pan with 1 tbsp icing sugar. Heat until juicy and then squash with a fork. Push through a sieve. Serve the cheesecake with the raspberry sauce and raspberries.