In a large bowl, combine the flour and sugar. Add the cubed butter and mix until the mixture resembles coarse crumbs.

Stir in the egg yolk and enough ice water to form a dough. Wrap the dough in plastic wrap and chill for about 30 minutes.

Preheat your oven to 375°F (190°C).

On a lightly floured surface, roll out the dough to fit your tartlet pans. Press the dough into the pans and trim any excess.

Place parchment paper in each crust and fill with pie weights or dried beans. Bake for about 15 minutes, then remove the weights and bake for an additional 10 minutes until golden brown. Let cool.

In a saucepan, heat the milk and cream until just about to simmer. In another bowl, whisk together the egg yolks, sugar, and cornstarch until smooth. Gradually add the warm milk mixture to the egg yolks, whisking continually.

Pour the mixture back into the saucepan and cook over medium heat, stirring continuously until thickened. Add the vanilla extract, then remove from heat.

Pour the custard into the cooled tartlet shells and let them cool completely. Top with mixed fresh berries before serving.

Garnish with mint leaves if desired. Enjoy these delightful treats with family and friends.