Make a buttery dough from the ingredients for the tartlets. Leave the dough in the fridge for about 20-30 min.
Make the cream by boiling the milk, adding the sugar and the starch you've beaten with a little cold milk.
Boil on medium heat while stirring nonstop to the desired consistency. Leave the prepared cream to cool. Add the butter and stir until homogenized.
Beat the liquid cream with a mixer until thickened. Carefully combine the 2 creams and stir until homogeneous.
Tear small balls from the buttery dough and spread them out in tartlet forms. Poke holes in the bottoms of the tartlets using a fork. Bake in a preheated oven until ready.
Take the baked tartlets out of the forms carefully, so they don't break because they're very fragile. Let them cool. Smear their bottoms with liquid chocolate. Fill the prepared tartlets with the prepared cream.