The scallops need not be pounded flat. Melt half the butter in a frying pan and cook the scallops for 3 minutes on each side, until golden brown. Season lightly with salt and pepper; remove and keep warm.

Brown the sliced onion lightly in the same butter. Sauté the mushrooms in the remaining 3 tablespoons butter in a separate pan. When some of their juice has evaporated, set them aside.

Pour the cider into the pan with the onion and deglaze it by boiling rapidly until about half has evaporated. Add the calvados and reduce a little more, then put in the mushrooms and the crème fraîche. Return the scallops to the pan, with any juice that has run out, season, and heat gently for 5 minutes. Serve with snow peas cooked quickly in butter and sliced apples sautéed in butter.