For the biscuit base:

1 Preheat the oven to 180 degrees, or 160 fan. Grease a 23cm round loose-bottomed spring form tin and line the base with a disc of parchment paper. Wrap two squares of tinfoil around the base of the tin and set aside.

2 Melt the butter in a small saucepan or in the microwave. Put the biscuits into a food processor with the sugar and blend to a fine powder. Alternatively, put the biscuits and sugar into a Ziploc bag and bash with a rolling pin until you have fine crumbs. Add the melted butter and mix well, then press into the base of the tin.

3 Use the back of a spoon or a spatula to smooth out the biscuit base into an even layer, then bake in the preheated oven for 15 minutes. Once baked, set it aside to cool while making the cheesecake filling.

For the cheesecake filling:

1 When ready to bake, turn the oven up to 210 degrees or 190 fan. Put the cream cheese into a large bowl with the sour cream and whisk for a minute or two until smooth. Alternatively you can do this in a stand mixer. Add the sugar, vanilla (seeds or extract) and lemon zest and whisk well to combine.

2 Add the eggs one by one and beat again until smooth. Sift in the flour with the salt and fold the flour through gently, making sure there are no little flecks of flour visible.

3 Pour the mixture into the prepared tin and smooth the top. Place the tin in a deep baking tray and place in the oven. Pour boiling water into the large tin, until it comes halfway up the cheesecake tin. Bake for 10 minutes, then reduce the oven temperature to 120 degrees, or 100 fan, and bake for a further 40-45 minutes. The cheesecake should have a slight wobble in the centre.

4 Turn the oven off and leave in the oven for two hours with the door slightly open for a perfectly creamy cheesecake. Chill the cheesecake in the fridge for at least four to six hours or overnight before serving.