Put the milk and sugar to boil and stir until the sugar melts. It's better to use a larger container so that it's easier to beat with a mixer later.
Beat the yolks with the flour and a little water. Once the milk comes to a boil, gradually add the beaten yolks with the flour, while still beating with the mixer.
Once you've beaten this cream well, leave it to boil 3-4 min. Next, add the butter and vanilla. Stir until the cream absorbs the butter.
In a suitable oven dish 10" x 10″ (27 cm x27 cm), arrange a layer of biscuits, pour on the warm cream, sprinkle with walnuts and continue until out of biscuits.
Sprinkle with the ground walnuts (can also use grated chocolate or colored sprinkles).
Keep in the fridge until it's time to serve.