In a food processor, blend the butter, powdered sugar, vanilla, salt and sifted flour at slow speed. Then knead the dough by hand on a floured surface and leave it in the refrigerator to set.
Roll out the dough on a floured surface, into a sheet with thickness of 1/4″ (0.5 cm). Using a metal disk or cup, cut out round slices, place them in greased and floured cupcake forms and arrange them in a tray.
Bake them in a preheated 428°F (220 °C) oven for 7-10 minutes. To prepare the cream, boil 2/3 of the milk, add the sugar, and once it comes to a boil, remove from the heat.
Whip the remaining 1/3 of the milk with the egg yolk and starch and pour it into the boiled milk in a trickle, while stirring constantly. Add 2 tbsp (30 g) of coconut flakes. Heat the milk to thicken the cream, while stirring constantly. Finally, sprinkle it with a little sugar, to prevent a crust from forming.
Melt the couverture chocolate. Coat the insides of the baked and cooled cups with it and leave them to cool. Distribute the cream using an icing piping syringe among the cooled cups.
Sprinkle the top with crumbled (not ground) walnuts and coconut flakes.