Black Bean and Sweet Potato Tacos with Avocado Crema

small or 1 large sweet potato

extra virgin olive oil

chili powder

homemade black beans or 2 cans black beans, drained

garlic powder (if using canned beans)

avocado

plain yogurt

freshly-squeezed lime juice (about ½ a lime)

garlic

salt and pepper

corn tortillas, depending on your eaters

Optional toppings:

Lettuce, tomatoes, purple cabbage, cucumbers, salsa, grated monterrey jack or cheddar cheese