Heat the oven to 200C (180C fan)/390F/gas 6.

Line a deep, 20cm, preferably loose-bottomed cake tin with baking paper, leaving some overhanging to help lift the cake out later (if you want a neater finish, grease the tin instead).

Put a roasting tray big enough to hold the tin on the middle shelf of the oven as insurance against leakage.

Put the biscuits in a zip-lock bag or similar, then whack them with a rolling pin – a mix of crumbs and slightly larger chunks is most interesting and appealing, so this is a better approach than using a food processor (although by all means pulse them in there instead, if you prefer). Note that you can vary the biscuits according to taste, so use chocolate, nut, shortbread, etc, as you see fit.

Melt the butter in a small pan or microwave, then stir in the crumbs and a good pinch of salt, and mix well to combine. Tip into the cake tin, then spread out to cover the base. Use the base of a glass, or similar, to press down firmly on the biscuit mix and create a solid layer, then bake for 15 minutes, until well toasted.

Meanwhile, put the cheese in a large bowl or food mixer – real cream cheese, without stabilisers, is often stocked in cheesemongers and kosher shops, and increasingly available in supermarkets (I especially like the Paysan Breton brand), but any full-fat sort should work fine. Just be sure to drain off any liquid before use.

Gently beat the cheese with a wooden spoon (or with the beater attachment of a food mixer on a slow speed) to soften and get rid of any lumps, while incorporating as little air into the mixture as possible. Add the soured cream, increase the speed of your arm or the mixer to medium and beat until completely smooth.

Mix the sugar and cornflour in a bowl, then add to the cheese mixture with the lemon zest, vanilla and a pinch of salt (or substitute other citrus zests or juices, flower waters, coffee or almond essence, etc) and mix briefly, again minimising the amount of air you introduce to the mix. Crack the eggs into a jug and beat, then gently mix into the cheese bowl at a low speed just until the filling is homogenous.

Take the base out of the oven and leave to cool a little. Turn down the oven to 120C (100C fan)/250F/gas ½ (it may help to leave the oven door open for a little while, to speed up cooling). Alternatively, make the base ahead of time and leave it to cool completely before adding the filling.

Once the oven is at temperature, pour the filling into the cake tin on top of the base, then shake gently to level it out. Run a spoon across the surface to get rid of any air bubbles, then carefully place the tin in the larger dish and bake for about 90 minutes, until set but gently wobbly in the centre – check regularly towards the end of the cooking time.

Turn off the oven and leave the cake inside to cool completely before unmoulding from the tin – this will help prevent the filling from cracking. Chill to facilitate even neater cutting, or serve at room temperature with some fruit of your choice – depending on the season, I like sliced oranges or fresh raspberries). The cake keeps well in the fridge for several days.