In a food processor bowl, combine flour, salt, sugar – pulse a few seconds.
Add cubed chilled butter – pulse for 30 seconds to a minute until it resembles bread crumb consistency.
Add the egg yolk – and pulse some more.
Add 2 to 4 tablespoons water until the mixture forms a dough.
Transfer to a work surface – bring the dough together to form a disc.
Wrap in cling wrap and chill in the fridge for about 15 minutes.
When chilled, roll small pieces of dough into disc and line each tart shell. Cut off any excess at the edges.
Alternatively, you can cut a small disc for the base of the tart and strips for the sides. Cut off any excess.
Place the tartlet in the fridge while you preheat the oven.
Preheat the oven to 200 C / 400 F.
Prick the pastry all over with the tines of a fork or cocktail stick to prevent the dough from puffing.
Bake in the preheated oven – the 3-inch mini-tarts take 10 to 12 minutes while the 5-inch mini-tarts take about 12 to 14 minutes.
Cool the tarts completely before filling.