Preheat the oven to 350°F.
In a mixing bowl, combine the flour, softened butter, sugar, egg yolk, vanilla extract, and salt. Mix until a dough forms.
Divide the dough into 12 equal portions and press each portion into the bottom and up the sides of a muffin tin to form tartlet shells. Prick the bottoms with a fork to prevent bubbling.
Bake the tartlet shells for 15-18 minutes, or until lightly golden. Remove from the oven and let cool completely in the tin.
Once cooled, carefully remove the tartlet shells from the muffin tin. Fill each shell with pastry cream or vanilla pudding, smoothing it out with a spatula.
Top each tartlet with a variety of fresh fruit, arranging them as desired.
If using apricot jam, heat it slightly in a microwave until melted and brush it over the fruit for a shiny finish.
Chill the tartlets in the refrigerator for at least 30 minutes before serving to allow the flavors to meld.