Mix the flour, sugar, and salt in a large bowl. Rub in the cold butter until the mixture resembles coarse crumbs. Add the egg yolk, then gradually mix in the cold water until the dough just comes together. Shape into a disc, wrap, and chill for at least 1 hour.

Heat the milk until steaming. Whisk the egg yolks, sugar, and cornflour until smooth. Slowly whisk in the warm milk, then return the mixture to the saucepan. Cook over low heat, stirring constantly, until thick and glossy. Remove from the heat and stir in the vanilla and butter. Cover the surface and cool completely.

Preheat the oven to 180°C. Roll the chilled dough to about 3mm thick and cut circles slightly larger than your mini tart tins. Press the dough into the tins, prick the bases, and line with baking paper and baking beans. Bake for 15 minutes, remove the weights, then bake for another 8–10 minutes until lightly golden. Cool completely.

Spoon the cooled custard into the tart shells and spread evenly. Arrange the peach slices in overlapping circles. Warm a little apricot jam and gently brush it over the peaches.

Refrigerate the assembled tarts for at least 1 hour before serving. Serve cold with whipped cream, vanilla ice cream, or on their own.