Preheat the oven to 325 degrees F.
Mix the chili powder, salt, oregano and pepper together in a small bowl. Sprinkle the cubed pork chunks with the spice mixture and put into a large Dutch oven. Add 1 cup of the salsa verde, chicken broth, garlic and onions. Stir together with a wooden spoon. Put the pot on high heat and bring the mixture to a simmer. Transfer to the oven and cook, covered, until the pork is tender and easily shreds, about 1 hour 45 minutes. Once done, shred the pork in the Dutch oven with a pair of tongs or 2 forks.
Turn the oven up to 350 degrees F.
Combine the remaining 2 cups salsa verde and sour cream in a wide, medium bowl. Spread about 1/2 cup of the mixture on the bottom of a large rectangular casserole dish.
Wrap the tortillas up in a damp paper towel and microwave 40 seconds. Lay the warm tortillas out on your cutting board. Dip into the sour cream-salsa mixture and fill evenly with the shredded pork mixture and sprinkle of the cheese. Roll the enchilada up and place seam-side down in the baking dish. Pour the remaining sauce over the top and top with the rest of the cheese. Bake 30 minutes. Garnish with cilantro sprigs, if using.
Recipe courtesy of The Neelys