1. Melt the butter and pour onto the cracker crumbs and mix well. Press into the bottom of a 9-inch spring form pan. Bake at 325F until the crust is set, about 10-12 minutes. Allow to cool.
 
2. In a large bowl beat the cream cheese with the flour, caster sugar, eggs, soured cream and vanilla extract with an electric mixer until light and fluffy.
 
3. Pour the mixture into the pan and bake for 35-40 minutes until set. Remove from the oven and leave to cool.
 
4. Heat half the blueberries in a pan with 2 tablespoons icing sugar and stir gently until juicy. Squash the blueberries with a fork then continue to cook for a few minutes. Add the remaining blueberries, remove from the heat and allow to cool.
 
5. Pour the blueberries over the cheesecake just before serving.