Encremadas (Creamy Tomatillo Enchiladas)

Steps

1. Place tomatillos, serrano peppers, and garlic in a saucepan, cover with about 4 cups water, and cook over medium heat for 15 minutes until softened.
2. While the salsa ingredients cook, heat half the oil in a medium frying pan over medium-high heat.
3. Fry tortillas one by one on both sides until soft and pliable, not crispy, adding more oil as needed. Set aside on a plate.
4. Let the cooked tomatillos cool slightly, then blend with the peppers, garlic, and ¼ cup of the cooking water until smooth.
5. Add the sour cream to the blender and puree again until you have a smooth, light green sauce.
6. Drain excess oil from the frying pan, then pour in the sauce and warm over medium-low heat.
7. Dip each tortilla in the warm sauce, fold in half, and place on a serving plate, 3 per plate. Add more tomatillo cooking water to the sauce if it thickens too much.
8. Top each serving with crumbled cheese, and garnish with avocado and onion slices.