In a medium bowl, mix the first 5 ingredients (beef through chipotle chillies). Form beef mixture into patties. Heat grill to high heat and place burgers on the grill.
Cook for 10 minutes on each side, until burgers reach desired level of doneness.
In a large skillet, over medium heat, heat coconut oil. To the skillet, add the onion and sweet potato.
Season with sea salt and freshly ground black pepper to taste and cook for 5 minutes, until vegetables are tender.
Place burgers on lettuce leaves and top with sautéed onion and sweet potato. Serve warm.