Preheat and Prep: Heat your oven to 160°C (140°C fan). Line the base of a 23cm springform tin with a circle of parchment paper. Smear a little butter around the sides of the tin — this helps the cheesecake release cleanly later.

Make the Base: Tip the digestive biscuits into a sealed bag and bash them with a rolling pin until you have fine crumbs that feel like damp sand. In a bowl, mix the crumbs with the melted butter and 1 tablespoon of sugar until it looks like wet, dark brown sand. Press this mixture firmly into the base of your tin using the bottom of a glass. You want an even, compact layer. Bake for 10 minutes until it smells toasty and feels set to the touch. Set aside to cool.

Start the Filling: In a large bowl, beat the cream cheese with an electric mixer on low speed until it’s completely smooth — about 1 minute. You should see no lumps at all, just a pale, silky mass. Add the 200g of sugar and the flour, beating until just combined. The mixture will look slightly grainy at this point, and that’s fine.

Add the Eggs: Beat in the vanilla extract, then add the eggs one at a time, mixing on low after each addition. The batter will become glossy and smooth, with a slight sheen. Scrape down the sides of the bowl between each egg to keep everything even. Finally, add the egg yolk and mix gently.

Finish the Filling: Fold in the soured cream and lemon juice with a spatula. The batter will now be thick, luscious, and pourable — it should look like a very thick custard, pale and creamy. Pour the filling onto the cooled base. Give the tin a gentle tap on the counter to release any air bubbles.

Bake to Perfection: Place the tin on a baking tray and bake for 50-55 minutes. The edges should look set and slightly puffed, while the centre will still wobble like a jelly when you gently shake the tin. The surface should be a pale gold, with no browning. Turn the oven off, crack the door open slightly, and leave the cheesecake inside for 1 hour. This gentle cooling prevents cracking.

Chill and Serve: Remove from the oven and run a thin knife around the edge of the tin to loosen the cake. Let it cool completely on a wire rack — about 2 hours. Then, cover loosely with cling film and refrigerate for at least 4 hours, ideally overnight. The texture firms up beautifully as it chills. Slice with a hot, dry knife for clean edges.