How to make
Heat the butter in a saucepan of the stove and fry the flour in it, stirring for 1-2 minutes.
Gradually and slowly top up the water with continuous stirring with a wire whisk. Finally, season with salt, black pepper, nutmeg and add the crushed walnuts.
The stirring continues until the walnut sauce thickens. Once removed from the stove, you can blend it to get the most fine sauce.