Put the sugar and 3 1/3 cups (800 ml) milk in a pot. I used milk and eggs from free-range animals, hence how the dessert looks.
Put it on the stove to boil, while stirring. You have to wait for the sugar to melt.
Beat the milk, 3 eggs and the flour in a dry bowl with a mixer; it needs to turn smooth and without lumps. Once the milk comes to a boil, take it off the stove and in a thin trickle, while stirring nonstop with a suitable spoon, pour in the egg mixture to the milk.
Return to the stove again and stir quickly and energetically, so it doesn't form an unpleasant crust at the bottom and so it doesn't burn. Remove it from the stove. Add the 2 vanillas for flavor and stir.
Finally, stir with about 3 1/3 tbsp (50 g) butter to improve the taste even more. Stir again.
Pour into cups and serve.