Baked Chocolate Cheesecake

Preheat the oven to 170°C/gas mark 3.

Melt the chocolate and 125g of sugar in a bain-marie (a bowl suspended over a pan of simmering water). Set aside to cool slightly.

Meanwhile make the biscuit base by mixing together the crushed digestives, melted butter and sugar. Press into a 20cm spring-form tin.

In a large bowl, beat the cream cheese, remaining caster sugar, soured cream, vanilla extract and eggs until well-mixed.

Pour half the mixture into the bowl with the melted chocolate and mix in thoroughly.

Spoon in alternate amounts of the plain vanilla mixture and the chocolate one onto the biscuit base. Bake for 50 minutes until firm, cool before serving.