You call it White Sauce or Roux. I call it Béchamel and I love it. It’s the basis of so many delicious dishes (lasagnes, gratins…)
Here’s a quick how to.
1 pint of milk, 20 g plain flour, 40 g unsalted butter, salt, pepper and a good pinch of grated nutmeg.
Melt the butter gently. As soon as it’s melted add the flour. Stir to make a smooth shiny paste. Slowly begin to add the milk. Just a little bit at a time and keep stirring until it’s all incorporated. You are looking for a thick consistency. Season to taste and add the nutmeg.
If you want to make it extra rich you can add a couple of spoon of creme fraiche and some grated cheese depending on the recipe.