To prepare a corn and grilled sweet potato chowder barbeque recipe, you will first need to prepare the sweet potatoes. Peel and cut the Sweet Potatoes in half lengthwise. Cut the corn into bite-sized pieces and place them on skewers. Heat the barbecue sauce over medium-high heat. Add the chopped onions and garlic and cook until the onions are translucent, about 5 minutes. Remove the onion mixture from the heat and set aside. In the same skillet, heat the remaining ingredients until they are heated through. Stir in the shredded Sweet potato and corn. Cook, stirring frequently, for about 3 minutes, until all the ingredients are coated with the sauce. Season with salt and pepper to taste. Serve with sour cream or guacamole.