Glaze the onion slices in clarified butter over a medium flame for 3 - 4 minutes.
Meanwhile, lightly beat the eggs in a bowl with the crème fraîche, salt and pepper. Pour the egg mixture over the onions.
Let it stand for 3 minutes if the flame is not too high. Spread the sausage slices over the top and cover and let stand for another 3 minutes at a low flame.
Serve with a green salad and fresh baguette or pain de campagne.