Preheat the oven to 350 degrees. And, grease a 9x11 baking dish with butter.
Begin by making the enchilada filling: In a large skillet, on medium heat, heat the oil. Add the sweet potatoes, garlic, pepper, garlic powder, cumin, salt, and chili powder and cook until the potatoes are tender, about 15 minutes. When they're tender, place them to a bowl and add the cheddar cheese and cream cheese.
Next, make the Green Chile Sauce: In a large skillet on low heat, heat the oil and cook the onion and garlic until soft, for about ten minutes.
Add the tomato, green chiles, chicken stock, heavy cream, and spices. Simmer ten minutes, or until the sauce thickens up a little bit. Remove the sauce from the heat and stir in the cheese.
Fill each tortilla with some of the filling, and roll it up. Place them close together in the baking dish, seam side down. Pour the Green Chile Sauce over the tortillas and then sprinkle on the Monterey pepper jack cheese. Bake for twenty minutes.
Top the enchiladas with the sour cream, tomatoes, avocados, cilantro, and jalapeno.