Rub the butter well with the flour, add the egg yolk, salt. Then to form the final dough, pour water little by little, until the dough is of normal consistency, not to stick to your hands.
It is not necessary to use all the water.
Careful! I made the dough in the picture with a double amount of ingredients, because the shape of the tarts is bigger. Normally use the amount of ingredients in the recipe.