Prepare the tin and preheat the oven. Set your oven to 160°C (140°C fan). Grease a 23cm springform tin and line the bottom with a circle of baking paper. Wrap the outside of the tin tightly with two layers of foil — this keeps the water bath from seeping in.

Make the biscuit base. Put the digestive biscuits into a sealed bag and crush them with a rolling pin until they look like coarse sand — you want fine crumbs with no large chunks. Mix the crumbs with the melted butter and sugar until the mixture feels like damp, clumping sand when pressed between your fingers. Tip it into the prepared tin and press it firmly and evenly across the base. Use the bottom of a glass to get it flat. Bake for 10 minutes — the kitchen will smell warm and toasty — then set aside to cool completely.

Beat the cream cheese. In a large bowl, beat the cream cheese with an electric mixer on medium speed until it's smooth and velvety — about 2 minutes. You should see no lumps at all, and the texture will feel light and airy. Add the sugar and flour, then beat again until fully combined, scraping down the sides of the bowl.

Add the eggs one at a time. With the mixer on low speed, add the eggs one by one, mixing just until each yolk disappears into the batter. Overmixing at this stage incorporates too much air, which can cause cracks later. The batter should look thick, glossy, and pale yellow — it will smell sweet and creamy.

Fold in the sour cream and vanilla. Pour in the sour cream, double cream, and vanilla extract. Use a spatula to fold them in gently, until the batter is completely uniform and smooth. It should feel heavy and silky as it moves in the bowl. Pour the batter over the cooled biscuit base, and give the tin a gentle tap on the counter to release any trapped air bubbles.

Bake in a water bath. Place the foil-wrapped tin into a larger roasting dish. Carefully pour boiling water into the roasting dish until it reaches halfway up the sides of the springform tin — this creates a humid, gentle environment that prevents cracking. Bake for 55–65 minutes. The edges will look set and pale gold, but the centre should still wobble like jelly when you gently shake the tin. The aroma filling your kitchen will be nutty, buttery, and faintly tangy.

Cool slowly in the oven. Turn the oven off and crack the door open slightly. Let the cheesecake sit in the cooling oven for 1 hour — this gradual cool-down stops the top from cracking. After an hour, take it out of the water bath, remove the foil, and let it come to room temperature on the counter. The surface will look smooth and slightly matte.

Chill overnight. Cover the tin with cling film and refrigerate for at least 6 hours, ideally overnight. The texture firms up beautifully — my kids absolutely devour this every time I make it, and waiting is the hardest part!