Invented by chef François Pierre La Varenne (1615–78) and named after his boss, Nicolas Chalon du Blé, Marquis d'Uxelles, duxelles means finely chopped mushrooms of any sort. They are generally dehydrated in advance to remove all their moisture, then mixed with chopped shallots, parsley or thyme, and sautéed in butter.
Duxelles is often used as a savoury pastry filling and is an essential ingredient in bœuf en croûte—the French take on beef Wellington.
Image by Jerry Pank