Preheat oven to 425°. Cut sweet potatoes in half lengthwise (peel first if desired). Place potatoes cut side down in a baking dish, drizzle well with olive oil and season well with salt and pepper. Roast for 25-30 minutes until easily pierced with a fork, turning potatoes over about halfway through.
When potatoes are about 8 minutes from being done, heat 1 tbsp olive oil in a small saucepan over medium heat. Add sliced shallot and chili and saute for a minute until soft. Add 1 can rinsed and drained black beans. Season with 1 tsp cumin, salt and pepper. Stir and reduce heat to low. (Don't start the beans too early on they will dry out.)
Microwave one unhusked ear of corn for 1 min, 30 seconds. Using a dish towel to handle the hot corn, carefully husk the corn and cut kernels off. When potatoes are just about finished, heat a small saute pan over medium-high heat. Add 1 tbsp olive oil and wait 30 seconds. Add the corn and season well with salt and pepper. Allow corn to sear for about a minute then toss it and leave for another minute or so. Remove from heat.
When potatoes are nice and soft, remove from oven. Divide potatoes between serving plates, top each with half of black beans, corn, avocado, crumbled cheese and cilantro. Crumble corn chips on top. Put a dollop of Greek yogurt on the side. Squeeze the juice of 1 lime evenly over each dish and serve.