Preheat the oven to 425 degrees and line a baking sheet with a silicone mat or parchment paper if you want to make cleanup easier.
In a medium bowl, toss the sweet potatoes with the oil, chili powder, cumin, and ¼ tsp. salt and pepper.
Spread the potatoes evenly on the baking sheet, making sure they are in one layer. Cook them for 15 – 20 minutes until they are fork tender.
Place the beans in a small pot, heat over a medium-low heat, and add the garlic powder and ¼ tsp. salt and pepper. Keep warm, covered, over a very low heat, stirring occasionally, until everything else is ready.
Cut the avocado in half and remove the pit. Scoop out all the avocado flesh and place it in a bowl if using an immersion blender or a blender if using a regular blender. Add the yogurt, lime juice, and garlic. Puree until smooth and then add 1/8 tsp. salt and pepper.
Wrap the tortillas in a damp cloth or paper towel and microwave for 30 seconds, or until warmed through.
Bring the potatoes and the beans to the table and let everyone design their own tacos with the avocado crema, cheese, and other toppings, as desired.