This is a traditional roast chicken dish from Algeria. The sauce is a combination of onions, garlic, mustard, balsamic vinegar, and cayenne pepper. When I have time, I prepare the chicken a few hours ahead of time and let it marinate in the sauce before roasting it in the oven. I usually serve the chicken with cubed roast potatoes. I coat them with the same sauce and cook them in the oven for 1 hour.