Preheat the oven to 450°F. Wash and dry the sweet potatoes. Wrap each sweet potato in a damp paper towel. Microwave on high 9 to 11 minutes, or until slightly tender when pierced with a fork. Place the beef in a bowl; season with salt and pepper. Gently mix to incorporate. Form the mixture into two 1/2-inch-thick patties; season on both sides with up to half the spice blend (you will have extra). Transfer the seasoned patties to one side of the tray. Add the partially cooked sweet potatoes to the other side of the tray. Drizzle with olive oil; season with salt and pepper. Bake the tray, uncovered, 10 minutes. Leaving the oven on, remove from the oven.

Carefully flip the partially cooked patties; evenly top with the cheese. Return to the oven and bake, uncovered, 5 to 7 minutes, or until the sweet potatoes are tender when pierced with a fork, the cheese is melted, and the patties are cooked through.* Remove from the oven. 

*The USDA recommends a minimum safe cooking temperature of 160°F for beef.

Meanwhile, if necessary, halve the buns. Wrap the halved buns in foil and place directly onto an oven rack; warm 5 to 7 minutes, or until heated through. Remove from the oven. Assemble the burgers using the warmed buns, barbecue sauce, finished patties, pickles, and crispy onions or shallots. Carefully halve the baked sweet potatoes lengthwise. Serve the burgers with the baked sweet potatoes. Garnish the sweet potatoes with the sour cream and as much of the pepper as you'd like, depending on how spicy you'd like the dish to be. Enjoy!