Place the milk and custard powder in a medium-sized saucepan.
Stir the ingredients well with a wooden spoon until you obtain a homogeneous mixture.
Add the sugar and vanilla, stirring quickly until the ingredients boil.
Leave the mixture on the fire, stirring constantly, until it thickens.
Remove the custard mixture from the heat, distribute it into serving cups, then leave it aside until it cools.
Distribute the biscuits on top of the custard, then place the cups in the refrigerator until they freeze before serving.