In a pan, sift the yolk and add the milk and cornstarch.
Mix until the starch completely dissolves, then add the rest of the ingredients.
If it's made from chopped walnuts or shredded coconut, add a cup, and if it's made from chopped dark chocolate, add half a cup.
Cook over low heat, stirring constantly until thickened.
Wait for it to cool, and if necessary add a little cream to improve the texture.
The indication is to make a pie with two layers of different flavors.
Example: Chocolate with Strawberry and Coconut, Chocolate with Strawberry and Walnuts, Coconut and Walnuts