Heat the oven to 425°F (220°C). Arrange the tomatillos, poblanos, onion, and garlic on a sheet pan and roast until charred and tender, 20 to 25 minutes.
Peel the garlic and transfer the roasted vegetables to a blender with the stock, cilantro, cumin, and salt. Blend until smooth.
Cook the sauce:
Heat the oil in a skillet. Pour in the blended sauce and simmer for 8 to 10 minutes until slightly thickened. Taste and adjust the seasoning.
Roll and bake:
Heat the oven to 375°F (190°C). Dip each tortilla in the warm sauce, fill with chicken, roll, and place seam-side down in a baking dish.
Cover with the remaining sauce and bake for 15 minutes. Finish with crema, queso fresco, cilantro, and lime.
Notes
For a milder sauce, remove the poblano seeds before roasting.
Warm tortillas briefly in a skillet or microwave so they roll without cracking.