Rognons au Porto “La Paillote”

• 4 calf’s kidneys
• 2 tablespoons butter
• ½ Spanish onion, finely chopped

Free kidneys of fibres and fat; slice thinly. Melt butter in a frying pan; when butter is sizzling, add sliced kidneys. Then add finely chopped onion and parsley, and sauté, stirring constantly, for a few minutes. Season to taste with salt and freshly ground black pepper. Add sliced mushrooms and continue cooking, stirring continuously. Add flour; stir in port; and cook until well blended. Serv