Melt the butter gently in a small pan on a low heat. Roughly break up the biscuits and and place them in a food processor. Process the biscuits for 2-3 minutes until they resemble fine crumbs. Add the sugar, then pour in the melted butter and process for 30 seconds to combine
Put the biscuit mixture into the base of the tin, using the back of a tablespoon to smooth the surface evenly. Place in the fridge for 30 minutes
Rinse out the processor bowl. Place the cream cheese and sugar in the bowl and process for 2-3 minutes. Add the eggs, one at a time, beating well after each addition. Add the cornflour, sour cream and vanilla essence and process for 30 seconds to combine
Pour the filling into the tin and bake in a low oven at 150°C for 1 hour. When cooked, the cheesecake should be well-risen, with a golden brown top. It should feel slightly firm to the touch - if the mixture still appears wet, continue to bake a little longer. When cooked, turn off the oven and allow the cheesecake to cool in the oven, with the door ajar. When completely cool, place in the fridge. Serve with summer berries and pouring cream
Cooking the cheesecake in a bain marie or using a Wilton Bake-Even Strip stops the top from cracking