This looks like a lot of onions, but it cooks down to a mere 3 cups. Unbelievably delicious on hot dogs. Can, also, be use to top hambugers, sliders, flank steak, frajitas and the list goes on. Refrigerate leftovers.
In a large skillet, melt butter and oil over medium heat. Add onions and cook, tossing frequently, 20 to 25 minutes or until onions are golden. Stir in chipotle chile, brown sugar, salt, and pepper and cook 5 minutes longer to let the flavors blend.