The only heat you’ll need for this fresh, no-cook salsa comes from serrano peppers. Creamy avocado combines with juicy tomatillos to make this addictive, versatile sauce, which you can dollop on eggs, tacos, or anything else that needs a burst of flavor.
Remove and discard the papery husks from the tomatillos; cut each in half and remove the hard parts surrounding the stem. Trim away and discard roots and tough stems from cilantro. Place tomatillos and cilantro in a blender along with lettuce, serrano peppers, and garlic clove. Slice the avocado open vertically, and twist the halves apart. Carefully whack a knife into the pit, twist to loosen, and remove the pit. Gently run a spoon between the flesh and the skin of the avocado until the flesh comes out in one piece. Repeat with the other half. Into the blender, add avocado halves, juice from the lime, and shallot.
Blend to a chunky purée, 30 seconds, adding ½ teaspoon salt halfway through with the motor running. Taste and add remaining salt (or more) as needed. Makes about 2 cups Salsa Verde. (Store in airtight container for up to two days in the refrigerator.)