1 tablespoon vegetable oil
1 onion, chopped
4 cloves garlic, minced
6 cups canned kidney beans, drained
2 cups water
3 tablespoons chili powder
2 teaspoons ground cumin
4 teaspoons prepared mustard
1 pinch cayenne pepper, or to taste
3 tablespoons soy sauce
4 cups cooked and mashed sweet potatoes
12 (10 inch) flour tortillas, warmed
8 ounces shredded Cheddar cheese