Whisk flour and egg yolks in a large bowl until smooth.
Boil milk and sugar slowly in a pan.
Pour hot milk into the egg mixture while stirring constantly and return to the pan.
Stir over low heat until the crème pâtissière thickens and set aside.
Preheat the oven to 200°C.
Roll out pastry, prick with a fork, cut 15cm rounds, and chill for 15 minutes.
Place pastry rounds onto a lightly greased baking sheet.
Brush pastry edges with egg and spread crème pâtissière in the centers.
Top with sliced peaches and drizzle with melted butter.
Bake the tarts for 8 to 10 minutes.
Pulse crumble ingredients in a food processor until breadcrumb texture is achieved.
Sprinkle crumble over tarts and bake for another 15 minutes until golden.
Serve warm with vanilla ice cream and fresh mint.