1 Chop the chiles and garlic roughly, and place in a blender jar. Blitz until mostly chopped.
2 Cut the tomatillos in half and add to the blender jar with the water. Liquefy until the salsa transforms into a thick, chunky sauce.
3 Pour into a bowl and stir in the onion and cilantro. Taste and see if you like it as is, or if you'd prefer more acidity or salt. If so, add the lime juice and taste again. Then stir in the salt and taste one more time, adding more salt, if necessary. Top with the avocado, if using, just before serving.
4 Salsa (minus the avocado) keeps for about a week in a sealed container in the fridge.
VARIATION: To make another version of green salsa that's typical of street stands, blend the avocado with the onion and cilantro. Then taste for lime juice and salt, and blend again. COOKING TIP: As with every salsa in Mexico, it's really the cook's touch that gives it personality. Feel free to add more water if you want it thinner, and-even though some Mexicans probably wouldn't agree-you can even omit the salt, which creates a brighter, sweeter salsa that's almost like a relish. If you own a powerful blender, no need to chop anything first. Just toss it in the blender jar whole.
"Eat Mexico" by Lesley Tellez (c) Kyle Books 2015. Provided courtesy of Lesley Tellez. All rights reserved.