Preheat the oven: Heat the oven to 350°F.
Make the pumpkin sauce: In a medium bowl, combine the pumpkin puree, chili powder, cumin, coriander, cinnamon, chicken broth, and Greek yogurt. Stir until smooth. The sauce should be thin enough to spread easily; add a little more broth or water if necessary.
Prepare the baking dish: Spread 1 cup of the pumpkin sauce evenly across the bottom of a 9 x 13-inch casserole dish.
Cook the sweet potato: Place the diced sweet potato in a microwave-safe bowl with 1 tablespoon of water. Microwave for 3–5 minutes, or until fork-tender.
Make the filling: Combine the cooked sweet potato, shredded chicken, green chilies, and half of the shredded cheese. Stir in 1/2 cup of the pumpkin sauce until everything is lightly coated.
Fill the tortillas: Divide the chicken mixture evenly among the 8 corn tortillas. Place the filling down the center of each tortilla, then roll them up.
Arrange the enchiladas: Place each rolled tortilla seam-side down in the prepared casserole dish.
Add the topping: Pour the remaining pumpkin sauce evenly over the enchiladas, then sprinkle the remaining cheese over the top.
Bake: Bake for about 25 minutes, until the cheese is melted and the sauce is bubbling around the edges.
Garnish and serve: Sprinkle with chopped cilantro and serve warm. These creamy pumpkin chicken enchiladas are especially delicious while the cheese is still bubbling and golden.