Preheat oven to 375 degrees Fahrenheit.

On a large baking sheet, spread sweet potatoes in a single layer and spray with cooking oil. Season with salt and pepper and bake for 20–30 minutes, until soft and slightly brown around the edges. Remove and set aside.

Raise oven temperature to 425 degrees Fahrenheit.

In a small food processor, blend avocado, cilantro, water, yogurt, lime juice, garlic powder, salt, and pepper until smooth. Set aside.

In a saucepan, heat oil over medium heat. Add shallots and cook until translucent. Season generously with paprika, garlic powder, cumin, chipotle powder, salt, and pepper. Add black beans and sweet potatoes, stirring to combine. Simmer about five minutes.

Using a potato masher or the back of a fork, partially mash the mixture, leaving some beans whole. Remove from heat.

Spray a baking dish with cooking oil. Working with one tortilla at a time, place about two tablespoons bean mixture on one half of the shell and sprinkle with cheese. Fold tortilla over and place in the prepared dish. Spray the top of the shell and repeat until all tortillas are filled.

If tacos remain folded, bake immediately for five minutes per side until cheese is melted and shells are crispy. If they keep opening, place another baking sheet on top of them and bake them like that, also for five minutes per side.

Serve with crema, lettuce, and tomatoes.