Recipe:

Slice 1/4 of onion into thin rings and set aside.

Tomatillo salsa:
1. Preheat broiler.
2. Husk 1 lb. tomatillos.
3. Place the other 3/4 onion, tomatillos, and serranos (2 + 1 jalapeno may be ideal?) on a foil-lined baking sheet and broil until the vegetables are soft and slightly brown, 7-10 minutes, turning as needed.
4. Transfer the vegetables and any liquid to a blender, add 1/2 tsp. salt, 1/2 tsp. cayenne (less / none if more peppers), and pinch of sugar, mash tomatillos manually in blender, and puree.  Add 1/4 cup chicken broth or water if necessary.

Enchiladas:
1. Stack the tortillas, wrap in a damp paper towel, and microwave just until warm and soft, 1 minute; keep covered.  Recommend 1 damp paper towel between each two tortillas.
2. Toss 3 cups shredded or diced rotisserie chicken with 2 cups Sargento shredded taco cheese in a bowl.
3. Spoon a portion of the chicken mixture (~3 heaping soup spoons) and re-blended tomatillo salsa (~1 soup spoon) down the middle of each tortilla and roll up.
4. Place the enchiladas side by side on a lightly oiled rack in a 9-by-13-inch baking pan and brush with 2 tbsp. olive oil.
5. Broil until crisp and golden, ~4 minutes (rotating as necessary).  Flip and broil the other side until quite crispy (~4 more minutes, rotating as necessary). [times are without brushing with olive oil - these may vary with that step included, and by oven)
6. Re-blend the tomatillo sauce and pour over the enchiladas.
7. Top with the remaining 1/2 cup shredded cheese.
8. Return to the oven and broil until the cheese is bubbly and golden brown, 3-5 minutes.
9. Top with the onion rings and feta.