Preheat the oven to 400° F. Line a large, rimmed baking sheet with parchment paper.
Slice the sweet potatoes in half lengthwise. Brush the cut sides lightly with olive oil. Place the sweet potatoes on the prepared baking sheet, with the flat cut sides facing down. Bake until tender, about 30-35 minutes. Remove the potatoes from the oven, leaving the oven on for baking the enchiladas.
As the potatoes cook, combine all of the remaining filling ingredients in a medium-sized mixing bowl.
Once the sweet potatoes are out of the oven and cool enough to handle, scoop out the potato pulp with a spoon; discard or compost the potato skins. Lightly mash the sweet potatoes with a fork or potato masher.
Stir the mashed sweet potato into the bowl of filling, and season to taste with additional salt (about ¼ tsp) and pepper.
Warm up your tortillas, either by spreading them on a baking sheet (overlapping slightly) and baking in the heated oven for 3-4 minutes or all at once in a microwave (for maybe 30-60 seconds?) so they don’t break when you bend them. Place them in a tortilla warmer or wrap them in a clean tea towel so they stay warm.
Cover the bottom of a 9x13-inch baking dish with a thin layer of the salsa verde (about ½ cup). Working with one tortilla at a time, spread about ½ cup of the filling down the center each tortilla, rolling up both sides over the filling; place in your baking dish. Repeat until you have filled all of the tortillas.
Pour the remaining salsa verde on top, and sprinkle with cheese. Bake for 25-35 minutes, until sauce is bubbling and the cheese is puffy and lightly browned.
As the enchiladas rest for a few minutes, make the crema. Whisk the sour cream and water together until smooth. Drizzle the crema over the enchiladas, then garnish with cilantro and red onion to taste.
Source: Cookie and Kate