Prepare the Base: Preheat your oven to 160°C (140°C fan). Crush the biscuits into fine crumbs. I like to put them in a sealed bag and use a rolling pin until you hear no more crunching. Mix with the melted butter and 1 tablespoon of sugar until the mixture smells deeply buttery and looks like wet sand. Press this firmly into the base of a 23cm springform tin. Bake for 10 minutes, until the edges are just beginning to turn a shade darker and you can smell toasted biscuit. Set aside to cool.

Start the Filling: In a large bowl, beat the room-temperature cream cheese with an electric mixer on low speed. You want it to look fluffy and feel light, like a cloud, with no lumps. This takes about 2 minutes. Scrape down the bowl and beaters thoroughly.

Add Dry Ingredients: Add the 250g sugar, flour, vanilla, lemon zest, and salt. Beat on low just until combined. The batter will look slightly grainy at this stage, but that’s fine. Stop as soon as you can’t see the sugar anymore.

Incorporate the Eggs: Add the eggs and egg yolks one at a time, beating on low after each addition. The batter will become increasingly smooth and glossy, turning a pale, creamy yellow. Do not overmix; you just want it to come together. Overbeating adds too much air, which causes cracking.

Finish with Soured Cream: Gently fold in the soured cream using a spatula. The batter should now be silky, thick, and luscious, with a slight sheen. Pour it over the cooled biscuit base. Give the tin a gentle tap on the counter to release any trapped air bubbles.

The Low and Slow Bake: Place the tin on a baking tray in the centre of the oven. Bake for 50 minutes. Then, without opening the door, turn the oven off and leave the cheesecake inside for another 1 hour. The top should be set and a pale golden colour, but the centre will still wobble like a firm jelly when you gently shake the tin. This is exactly what you want.

Cooling and Chilling: Run a thin knife around the edge of the tin to release the cake. Let it cool completely on a wire rack at room temperature for at least 2 hours. The smell of warm cheesecake will fill your kitchen. Once cool, cover loosely with cling film and refrigerate for at least 4 hours, but ideally overnight. This is where the magic of a firm, clean slice happens.