1. Preheat the oven to 350°F.

2. Place the sweet potatoes on a baking sheet and bake for 45 to 60 minutes, until they are tender when pierced with a fork.

3. While the potatoes bake, heat a large heavy skillet over medium-high heat. Add the corn in a single layer without oil. Season lightly with salt, and add the chili powder and cumin if using. Let the corn cook undisturbed for a few minutes at a time so it gets browned and a little charred. Stir occasionally and continue cooking for about 10 minutes total. Transfer the corn to a bowl and mix with the black beans.

4. In the same skillet, melt the butter over medium heat. Add the chopped onion and cook for 4 to 5 minutes, until soft and translucent. Remove from the heat.

5. When the sweet potatoes are done, let them cool for 5 to 10 minutes. Slice each one in half lengthwise. Carefully scoop out most of the flesh, leaving a thin layer inside the skins so they keep their shape.

6. Add the scooped sweet potato flesh to a bowl with the cream cheese, sour cream or Greek yogurt, chipotle peppers, and 1 teaspoon salt. Mash and stir until mostly smooth.

7. Gently fold in the black beans, roasted corn, cooked onion, and cilantro.

8. Spoon the filling back into the sweet potato skins. Sprinkle 1 tablespoon of shredded cheese over each half.

9. Place the filled skins under the broiler for about 5 minutes, or until the cheese is melted and bubbly. Serve warm.