For the shortbread base
200g (7 oz) unsalted butter, softened
225g (8 oz) plain flour
115g (4 oz) cornflour
150g (5½ oz) caster sugar
A little extra soft butter, for greasing
For the filling
800g mascarpone cheese
568 ml (1 pint) double cream
115g (4 oz) caster sugar
1 tsp vanilla paste or extract
For the topping
5 tbsp Crème de Cassis or blackcurrant syrup
25g (1 oz) caster sugar
1 tbsp arrowroot
2 tbsp cold water
1 tbsp lemon juice
250g (9 oz) fresh blueberries
150ml (5 fl oz) double cream, whipped
Fresh raspberry leaves
1. Lightly butter the sides and base of a 23cm (9 inch) spring-form tin and base line with baking parchment. Rub the butter into the flours until the mixture resembles breadcrumbs, then mix in the sugar. Tip into the tin and press down with the back of a spoon. Chill for 30 minutes before baking.
2. Bake on a grid shelf on the floor of the Baking Oven for 15-20 minutes until cooked and very pale golden, turning the tin half-way through cooking. Leave to cool in the tin on a cooling rack.
3. Mix the cheese, cream, sugar and vanilla in a bowl until thickened and turn into the tin and level off the surface. Cover and refrigerate for 4 hours.
4. To make the topping, place the Crème de Cassis in a stainless steel saucepan with the sugar and place on the Simmering Plate, stirring occasionally.
5. Slake the arrowroot in a cup with the cold water. When the sugar has dissolved in the pan, remove from the heat and whisk in the arrowroot mixture. Return to the Simmering Plate and stir until the mixture clears and thickens slightly.
6. Add the lemon juice and blueberries and stir as the mixture cools and thickens further. When almost cool, pour over the cheesecake and chill for a further hour.
7. Decorate before serving by piping an odd number of rosettes of whipped double around the cheesecake, topping these with leaves.