Start with at least a 2.5 quart stainless steel or enamel saucepan. Melt 1 tbsp. butter with shallots over medium heat. While butter is bubbling add garlic. Stir and use caution to avoid burning or scorching. Add tarragon, wine, broth, and vinegar. Continue to stir while bringing to a rolling boil over medium-high heat. Continue to boil to reduce volume to 1/2 or 1/3. This should only be 5 to 6 oz. Take off heat and strain liquid into another saucepan of at least the same size. Reheat over medium-low burner. Whisk in red enchilada sauce, chili powder, and cocoa powder. Be extremely careful to avoid scorching. Simmer about ten minutes to permit flavors to wed. Add remaining tbsp. of butter just before serving. Serve with your favorite steak.