Make the biscuit crust. Place the digestive biscuits in a sealed plastic bag and crush them with a rolling pin until you have fine crumbs with a few slightly larger pieces — you want a texture that feels like damp sand. Pour the crumbs into a medium bowl, add the melted butter and golden caster sugar, and stir until every crumb is coated. The mixture should clump together when you squeeze a handful.

Press the crust into the dish. Tip the buttery crumbs into a 23cm loose-bottomed tart tin or pie dish. Press the mixture firmly into the base and up the sides using the flat bottom of a drinking glass. You should hear a gentle crunch as the crumbs compact. Pop the dish into the fridge to firm up for 15 minutes while you make the filling.

Beat the cream cheese and peanut butter. In a large mixing bowl, beat the room-temperature cream cheese with an electric hand mixer until it is smooth and glossy — about 1 minute. Add the peanut butter and beat again until fully combined. Stop to scrape down the sides of the bowl; you should see a pale, fluffy mixture with no streaks of cream cheese remaining.

Add the sugar and vanilla. Sift the icing sugar into the bowl and add the vanilla extract. Beat on low speed at first to prevent a sugar cloud, then increase to medium speed for 30 seconds. The mixture will thicken slightly and smell wonderfully sweet and nutty.

Fold in the whipped cream. In a separate clean bowl, whip the 200ml double cream until soft peaks form — when you lift the whisk, the cream should hold a gentle curl that flops over. Gently fold this whipped cream into the peanut butter mixture using a spatula. Do not stir vigorously; you want to keep the air in the cream. The final filling should be light, mousse-like, and a pale caramel colour.

Assemble the pie. Spoon the filling into the chilled biscuit crust and spread it evenly with the back of a spoon. Tap the dish gently on the counter to settle the filling and remove any air pockets. Cover the pie loosely with cling film and refrigerate for at least 4 hours, but overnight is best. The surface should feel firm and slightly springy to the touch when set.

Make the chocolate topping. About 30 minutes before serving, make the topping. Place the dark chocolate in a heatproof bowl. Heat the 100ml double cream in a small saucepan until it just begins to simmer — you will see tiny bubbles around the edge of the pan, but do not let it boil. Pour the hot cream over the chocolate and let it sit for 2 minutes. Stir gently in one direction until you have a smooth, glossy ganache that coats the back of a spoon.

Finish and serve. Pour the ganache over the set pie and tilt the dish gently so it covers the entire surface in an even layer. Sprinkle the chopped peanuts and a pinch of flaky sea salt over the top. Return the pie to the fridge for 15 minutes to set the ganache. Slice with a warm knife for clean, sharp edges — the crust will shatter slightly as you cut, and the filling will be velvety smooth.