Frozen Caramel Cheesecake

SALTED CARAMEL SAUCE: Put the caster sugar and water in a clean pot over a medium heat and whisk to start dissolving the sugar. Use a small pastry brush to brush down any sugar that gets stuck to the side of the pot to stop it burning. Bring to a simmer, giving the pot a gentle swirl now and again to help it heat evenly.

As soon as the sugar is pale amber — it will first become white and crystallised, then start to clear and turn a pale golden amber — add the cream in two lots, whisking hard after each addition. The caramel will froth up madly but keep whisking and it will settle down. 

Whisk in the butter and salt and leave to cool.  Set aside in fridge. Reheat gently to serve.

EQUIPMENT: Line the base and sides of a 20cm springform cake tin with baking paper.

CHEESECAKE: Whiz the melted butter and half of the biscuits together in a food processor until it forms the texture of damp sand, then tip into the prepared tin. Squash the biscuit crumbs into the base of the tin, using a tablespoon to compact the base. Pop the base in the fridge for half an hour.

Put the caramel condensed milk, cream cheese, vanilla and egg yolk in a mixing bowl and, using electric beaters, whisk until smooth.

In another bowl, beat the egg white until stiff. Add the sugar and continue beating until glossy and smooth.

Fold the egg white mixture into the cream cheese mixture, then fold in the whipped cream.

Crush the remaining biscuits into chunks by putting in a sealed bag and banging with a rolling pin (deeply satisfying). Fold the biscuit chunks through the cheesecake mixture, then tip into the biscuit-lined tin. Smooth the top and sprinkle over the caramel popcorn. Freeze overnight.

TO SERVE: Remove the cheesecake from the freezer 15 minutes before you want to serve it, then top with a drizzle of caramel sauce, with more on the side.