First, make the pastry. Melt the butter in a saucepan until foaming, then sizzle until it turns nut-brown. Pour off the fat into a bowl, leaving the sediment in the pan to be discarded. Leave the fat to cool, then chill until it hardens again. Combine the flour, icing sugar and a pinch of salt in a medium bowl. When the fat has hardened, cut it into chunks and rub it into the flour mixture until crumbly. Stir in the egg yolk and 1 tsp cold water, and bring it together into a dough. Flatten into a disc, then cover and chill for at least 30 mins. Can be made up to two days ahead. (The pastry can also be made with regular butter.)

Roll the chilled pastry out on a lightly floured surface to a roughly 5mm thickness, then lift into a 20cm tart tin. Press the pastry into the base and up the side using a small piece of excess floured pastry. Leave some overhanging the rim. Chill for at least 30 mins, or freeze for 10 mins. Reserve any excess pastry.

Heat the oven to 180C/160C fan/gas 4. Line the pastry case with baking parchment and fill with baking beans or uncooked rice. Put on a baking tray and bake for 15 mins. Remove the parchment and beans and bake for 15-20 mins more until biscuity.

Meanwhile, make the filling. Tip the cream and vanilla into a saucepan and bring to the boil. Stir (don’t whisk) the egg yolks and sugar together in a heatproof bowl. Slowly drizzle the hot cream over the egg yolk mixture, stirring continuously (not whisking) until everything is incorporated. Sieve the custard through a fine mesh sieve into a jug, then spoon off any froth.

Remove the baked tart case from the oven, and reduce the temperature to 140C/120C fan/gas 1. Trim the excess pastry from the case, and mend any cracks with the reserved raw pastry. With the tart case on the baking tray, slide it halfway back into the oven, then carefully pour in the filling to the top of the case. Finely grate over at least half a nutmeg. Gently slide the tray fully into the oven and bake for 40 mins, or until just set with a very slight wobble. Leave to cool completely in the tin, then remove from the case and cut into slices.