Instructions

• Position an oven shelf in the middle of the oven
• Preheat the oven to fan 160C/conventional 180C/gas 4
• Line the base of a 23cm springform cake tin with parchment paper
• For the crust, melt the butter in a medium pan
• Stir in the biscuit crumbs and sugar so the mixture is evenly moistened
• Press the mixture into the bottom of the pan and bake for 10 minutes
• Cool on a wire rack while preparing the filling
• For the filling, increase the oven temperature to fan 200C/conventional 240C/gas 9
• In a table top mixer fitted with the paddle attachment, beat the soft cheese at medium-low speed until creamy, about 2 minutes
• With the mixer on low, gradually add the sugar, then the flour and a pinch of salt, scraping down the sides of the bowl and the paddle twice
• Swap the paddle attachment for the whisk
• Continue by adding the vanilla, lemon zest and juice
• Whisk in the eggs and yolk, one at a time, scraping the bowl and whisk at least twice
• Stir the 284ml carton of soured cream until smooth, then measure 200ml/7fl oz (just over 3⁄4 of the carton)
• Continue on low speed as you add the measured soured cream (reserve the rest)
• Whisk to blend, but don't over-beat
• The batter should be smooth, light and somewhat airy
• Brush the sides of the springform tin with melted butter and put on a baking sheet
• Pour in the filling - if there are any lumps, sink them using a knife - the top should be as smooth as possible
• Bake for 10 minutes
• Reduce oven temperature to fan 90C/conventional 110C/gas 1⁄4 and bake for 25 minutes more
• If you gently shake the tin, the filling should have a slight wobble
• Turn off the oven and open the oven door for a cheesecake that's creamy in the centre, or leave it closed if you prefer a drier texture
• Let cool in the oven for 2 hours
• The cheesecake may get a slight crack on top as it cools
• Combine the reserved soured cream with the 142ml carton, the sugar and lemon juice for the topping
• Spread over the cheesecake right to the edges
• Cover loosely with foil and refrigerate for at least 8 hours or overnight
• Run a round-bladed knife around the sides of the tin to loosen any stuck edges
• Unlock the side, slide the cheesecake off the bottom of the tin onto a plate, then slide the parchment paper out from underneath