A rich and complex tomatillo and chile base marries with warm spices and beer for this big-bowl crowd-pleaser. A dollop of cooling sour cream helps offset the heat.
Heat oven broiler. Place tomatillos, stemmed serranos, and poblanos on a foil-lined baking sheet and broil, turning as needed, until blackened, about 10 minutes. Transfer to a bowl and cover with plastic wrap. When poblanos are cool, peel, seed, and coarsely chop; set aside. Peel tomatillos and serranos and transfer to a blender. Add stock, cilantro, sour cream, salt, an