Start by making the tart dough. In a food processor, add the flour, powdered sugar, and salt, and mix until combined.

Add the cold cubed butter, and blend until there are pea-sized pieces of butter. If you don't have a food processor, you can do it by hand, mixing the cold butter into the flour mixture. Make sure that your hands are cold.

Then, add the egg, and the vanilla extract and mix until a dough forms. Try not to overmix the dough.

Cover the dough with plastic wrap and let it chill in the fridge for at least an hour.

Transfer the dough onto a clean floured surface and roll it with a rolling pin into a rectangle.

Use a cookie cutter or a round bowl (1 inch larger than the mini tart pans) and cut small rounds of the pastry.

Place the pastry inside the mini tart pans and press it down using your clean hands.

Cut off the extra edges. Make holes in the bottom of the pan with a fork and place them in the freezer for at least 20 minutes.

Bake in a 180c (350f) preheated oven for about 20 minutes or until the crust is a light golden brown color. Remove from the oven and let it cool while making the filling.