TO COOK SWEET POTATO IN THE OVEN: Preheat oven to 400 degrees. On a parchment paper lined baking sheet, toss sweet potato pieces with 1 teaspoon oil. Lay the pieces evenly across the baking sheet, making sure not to touch or overcrowd. Bake sweet potatoes for 20 minutes, stopping once or twice throughout the baking time to toss the potatoes for even browning. After 20 minutes, check to see if they're done - brown on the outside and soft on the inside. If not, cook 5 minutes longer. Once finished, remove from oven and set aside.
TO COOK SWEET POTATO IN AIR FRYER: Put sweet potato pieces into air fryer basket. Spray sweet potatoes with oil or toss with a teaspoon of oil. Cook at 400 degrees for 10 to 12 minutes, stopping once or twice to shake the basket.
While the sweet potatoes are cooking, in a large skillet, bring remaining half teaspoon of oil to a medium heat. Saute onions and garlic for a few minutes, until translucent and fragrant.
Add black beans, chipotle pepper in adobo sauce, cumin, paprika, ancho chili powder, salt, and agave or maple syrup to the skillet. Put 2 Tablespoons of water into the skillet and combine all of the ingredients.
Add the cooked sweet potatoes to the skillet and the remaining Tablespoon of water to fully incorporate all of the spices.
Taste for salt and add more if desired. If you'd like a spicier filling, add an additional chopped chipotle pepper or a half teaspoon of adobo sauce. Fully incorporate all of the ingredients in the skillet.
Now it's time to warm the corn tortillas. You can either microwave them to make them pliable OR warm them in a skillet.
TO WARM THE CORN TORTILLAS IN THE MICROWAVE: Put the corn tortillas on a plate, and cover them with a damp cloth napkin. Microwave the corn tortillas for about one minute, stopping once to flip the stack half-way through. (If they aren't pliable enough, microwave for 30 seconds more.) While you fill each tortilla, keep the remaining plateful covered with the damp cloth napkin to keep them warm and pliable.
TO WARM THE CORN TORTILLAS ON THE STOVE: Bring a non-stick skillet to a medium heat. Put one corn tortilla onto the skillet. Warm one side for a minute or so. Then flip the corn tortilla and warm that side as well. Once the corn tortilla is warm and pliable, move it to a plate. Put another corn tortilla onto the skillet. While the second tortilla warms, fill the first one. And continue until all of the tortillas are warmed & filled.
HOW TO FILL CORN TORTILLAS: Put 2 Tablespoons of sweet potato & black bean mixture in a single row across the tortilla. The row should be closer to one edge, off from center. Grab the end of the tortilla, and fold it over the row of sweet potato & black beans. Tuck it underneath the sweet potato mixture, so that it's firmly holding onto it, like a hug. Then continue to roll the tortilla, until it's shaped like a cigar. Now it's time to bake OR air fry the taquitos.
TO BAKE THE TAQUITOS: Bring the oven up to 420 degrees. Line the baking sheet with new parchment paper, or re-use the old parchment paper if it's still fine. Put the taquitos seam side down onto the baking sheet. Give the taquitos a quick spray of oil. Bake the taquitos at 420 degrees for 15 minutes. I don't recommend flipping them, because they may not be fully sealed yet. You'll know the taquitos are ready when the edges are turning brown, and the center of each taquito feels firm to the touch. Carefully remove them from the oven. They will be hot.
TO AIR FRY THE TAQUITOS: Put each taquito seam side down into the air fryer basket. You likely won't be able to fit all 10 to 12 taquitos into the air fryer basket at once. So you'll need to air fry in batches. Line the taquitos in an even layer in the air fryer basket next to each other, allowing some room for air flow. Don't stack taquitos on top of each other. They won't brown that way. Give the taquitos a quick spray of oil. Air fry the taquitos at 400 degrees for 9 minutes. I don't recommend flipping them, because they may not be fully sealed yet. You'll know the taquitos are ready when the edges are turning brown, and the center of each taquito feels firm to the touch. Carefully remove them from the air fryer. They will be hot.
Serve with guacamole, salsa, and/or vegan cheese dip.