In a large skillet, heat oil over medium-high heat. Add onion and seasonings; cook and stir until onion is tender, 5-7 minutes. Add garlic; cook 1 minute longer. If desired, add in tequila, stirring constantly., Transfer to a 4- or 5-qt. slow cooker. Add broths and sweet potatoes. Cook, covered, on low until potatoes are tender, 6-8 hours. Stir in chocolate until melted. Cool soup slightly. Process in batches in a blender until smooth. Serve with toppings as desired.