Briefly roast the tenderloin slices in hot fat on both sides and add the following mushroom dish on top: Soften the finely chopped onion in butter (1), bring to a boil in white wine, stir in the yolks, butter (2), juice of one lemon, salt and pepper. Continue to add wine and beat the mixture on the fire in a water bath until it thickens. Separately, steam the cleaned, sliced mushrooms and finely chopped shallots in butter with the white wine. In the meantime, prepare a light roux from the above ingredients, add the mushrooms and the sauce and bring everything to the boil again. Serve with chips or french fries.
Tip: Instead of clarified butter, you can use butter in most cases.