In a large skillet over medium to medium-high heat, melt butter and add onions, garlic, salt and pepper. Soften 6-7 minutes then add chipotle purée and tomato paste, stir a minute then add stock, Worcestershire, Tamari, vinegar and honey or sugar. Bring to a bubble, add meat and heat through.
Serve meat with taco fixings or on rolls with pickles and onion.