2. Heat oil and melt butter in deep-sided, 12-inch (~30 centimeter) sauté pan on medium-high heat. When the oil is hot, but not smoking, use tongs to add chicken skin side down.
3. Brown both sides until skin is golden brown and chicken is cooked, about 12-15 minutes. Remove chicken to a platter and cover loosely with aluminum foil to keep warm.
4. Pour out half of oil from pan, and use other half to brown shallots over medium-high heat. Slowly add vinegar and boil until reduced to almost a syrup. Add crème fraîche/cream and cook until blended and brown, about 5 minutes. Return chicken to pan to coat and heat.