Prepare the biscuit base. Place the digestive biscuits in a sealed freezer bag and crush them with a rolling pin until you have fine crumbs with no large chunks. Alternatively, pulse them in a food processor until they resemble sand. The mixture should feel uniformly gritty when rubbed between your fingers. Pour the crumbs into a large bowl and stir in the melted butter until every grain is moistened and the mixture clumps together when pressed.

Press the crust into the tin. Tip the buttery crumbs into your tart tin and press them firmly and evenly across the base and up the sides using the flat bottom of a glass or a measuring cup. The crust should feel compact and solid against your fingers, not crumbly or loose. Place the tin in the refrigerator to set for at least 30 minutes while you prepare the filling.

Beat the cream cheese base. In a large mixing bowl, beat the softened cream cheese with an electric mixer on medium speed until it is completely smooth, with no lumps visible. The texture should look like thick, glossy spread, pale and creamy. Add the sweetened condensed milk and continue beating until the mixture is homogenous and slightly thickened, about 2 minutes.

Add the lemon and aromatics. Pour in the freshly squeezed lemon juice, add the lemon zest, vanilla extract, and a pinch of salt. Mix on low speed until just combined. You will notice the mixture thickening almost immediately as the acid from the lemon juice reacts with the dairy. Stop as soon as it looks smooth and uniform; overmixing can cause it to separate.

Whip the cream separately. In a separate, chilled bowl, pour the cold double cream and add the sifted icing sugar. Whisk with clean beaters on medium-high speed until soft peaks form. When you lift the beaters, the cream should hold a gentle peak that droops slightly at the tip, with a luscious, airy texture. Be careful not to over-whip into stiff peaks or butter.

Fold the cream into the lemon mixture. Take a generous spoonful of the whipped cream and stir it into the lemon-cream cheese mixture to loosen it. Then, gently fold the remaining cream into the bowl using a spatula, cutting through the centre and bringing the mixture up from the bottom. Continue until no white streaks remain. The final filling should be pale yellow, incredibly airy, and smell intensely of fresh citrus.

Fill the crust and chill. Remove the set biscuit base from the fridge. Spoon the lemon filling into the crust and spread it evenly with the spatula, creating a smooth surface. The filling should be glossy and hold its shape without running. Cover the tart loosely with plastic wrap and refrigerate for a minimum of 4 hours, or ideally overnight. When fully set, the filling will feel firm to the touch and slice cleanly.