Prepare the muffin tin and preheat the oven. You will require a 12-hole deep muffin tin and a 10cm (4in) round cutter. Preheat the oven to 200°C/180°C Fan/Gas 6.

For the custard. Heat milk, cream, and vanilla in a saucepan until hand hot. In a heatproof bowl, whisk together the whole egg, egg yolks, sugar, and cornflour. Pour in the hot milk mixture, whisking until smooth. Return the custard to the saucepan, heat over medium heat, and whisk until it thickens to a custard consistency. Avoid overcooking. Spoon the custard into a bowl, cover with cling film, and let it cool.

Unroll and cut the pastry.  Unroll the pastry, cut it in half lengthways, stack the strips, and cut it in half widthways. Roll out one piece thinly to create a large enough pastry for 5 discs using a 10cm (4in) cutter. Repeat with the other piece, yielding 10 discs in total.

Assemble the tarts. Place the rounds in the muffin tin, pressing firmly up the sides and pricking the bases with a fork. Fill the pastry cases with the cold custard, top with apricot slices, and chill for 30 minutes if time allows. Sprinkle the demerara sugar over the tarts.

Bake. bake for 25–30 minutes until the pastry is golden and the custard is set. Cool slightly.

Serve. Brush melted jam over the tart tops before serving.