550g purple sweet potatoes (about 2 medium ones), cut in half lengthways
50g roasted and salted almonds, chopped
10g black sesame seeds, toasted
60g unsalted butter, melted
300g full-fat cream cheese
90g icing sugar, sifted
2 tbsp lemon juice (from 1-2 lemons)
2 tsp vanilla bean essence
240ml whipping cream
350g white chocolate chips
White chocolate shavings, to garnish
Heat the oven to 210C (190C fan) and line a round 23cm spring-form cake tin with baking paper.
Lay the sweet potatoes cut side down on an oven tray lined with baking paper, and roast for 30-50 minutes (depending on size), until very, very soft. When cool enough to handle, scoop out the flesh into a food processor – you should have 300g of cooked flesh. Blitz until very smooth, then refrigerate until cold.
While the potatoes are roasting, make the ganache, heat cream in a saucepan until nearly boiling; pour over white chocolate chips in a bowl. Let sit for 3 minutes. Stir until chocolate is completely melted. Cover and refrigerate until cool, about 4 hours.
Next make the biscuit base by putting the oreos and almonds in a food processor and blitzing until fine. Mix with the sesame seeds and butter, then spoon into the base of the cake tin, pressing it down firmly to form an even layer. Refrigerate while you get on with preparing the cheesecake mixture.
In a free-standing mixer, whisk the cooled purple potato with the cream cheese, mascarpone, icing sugar, two tablespoons of lemon juice and a teaspoon of vanilla until smooth, thick and well combined. Spread the cheese mix evenly over the biscuit base, then refrigerate for at least five hours, or overnight, until set.
When ready to serve, take the ganache out of the fridge and beat with an electric mixer until peaks form, then place in a piping bag fitted with a star nozzle.
Release the cheesecake from its tin and discard the paper, then place on a serving plate. Pipe rosettes all over the top of the cheesecake and garnish with shaved white chocolate, then slice and enjoy!