Preheat oven to 350 degrees. Prepare a 13" x 9" casserole dish by greasing and set aside.
In a skillet over medium heat, heat the olive oil. Add the sweet potatoes, onion and jalapeños in the oil and coat. Sprinkle the ground black pepper and sea salt over the mixture to combine.
Add the water. Cover the pot and cook until potatoes are crispy on the outside but cooked through on the inside, about 8 minutes, stirring often so that the onions don't burn.
Add the garlic, corn, black beans, cumin and chili powder and stir to combine with the sweet potato and onions. Lower heat to medium and cook for about 3-5 minutes. Stirring frequently.
Pour ¾ cup enchilada sauce on the bottom of the casserole dish and then assemble enchiladas. To assemble enchiladas, scoop the sweet potato black bean mixture evenly amongst the tortillas. Top with a tablespoon of enchilada sauce each and roll together tightly.
Add the rolled tortillas side by side to pack the casserole dish. Pour the rest of the enchilada sauce on top and the rest of the cheese.
Bake for 20 to 25 minutes in the oven. Remove and allow to cool slightly for about 2 minutes.
Garnish chopped tomatoes, avocados, green onions, fresh cilantro and serve immediately.
*Make enchilada sauce first thing.