Whisk the vegetable mixture with a blender until smooth, you can additionally rub the mixture through a fine sieve. Add salt to taste, if necessary, add salt and sprinkle with black pepper to taste.
If it seems to you that the sauce is not thick enough, you can thicken it with a teaspoon of potato starch, diluting it in a tablespoon of cold water, the sauce, at the same time, needs to be heated to a boil.