For the butter sauce, finely chop the onions or shallots. Heat butter in a saucepan and sauté the onions in it. Pour in white wine and reduce over high heat until there is only about 2-3 tablespoons of liquid.
Gradually stir in cold butter pieces with a whisk (assemble), season with salt and pepper. Do not boil up the butter sauce any more!
Preparation Tip:
The butter sauce refines especially cooked fish dishes as well as dishes of veal, pork and poultry meat, but also fine vegetables such as asparagus, cauliflower and spring onions.