Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
   1 1/2  pounds        tomatillos
   4                    serrano chiles +/-
   1                    garlic clove -- peeled and
                        - roughly chopped
     1/4  cup           cilantro -- roughly chopped
   2      tablespoons   lard or safflower oil
   3      tablespoons   finely chopped white onion
                        sea salt to taste
   6      ounces        chicharron* -- broken into
                        - squares abut 1 1/2 inches

Preparation:

* chicharrón [chee-chah-RROHN] This crispy rich snack is made from pork skin that has been deep-fried twice, once in 325F oil, then again in 375F oil, making it balloon into a honeycombed puff. It is available in Latin American markets. Remove the husks from the tomate verde and rinse will. Put into a saucepan with the fresh chiles, cover with water, and bring to a simmer. Continue simmering until soft but not falling apart, about 10 minutes. Drain the tomate verde and transfer with the chiles and 1/4 cup of the cooking water to a blender. Add the garlic and cilantro and blend until smooth. Heat the lard in a frying pan, add the onion, and fry gently, without browning, for 1 minute. Add the blended sauce and fry over high heat, stirring from time to time, until reduced and thickened - about 7 minutes. Add salt to taste and the pieces of chicharron and continue cooking over medium heat until the chicharron is just soft - about 5 minutes, depending on thickness and quality. Serve with corn tortillas and a dollop of frijoles refritos. Source: The Art of Mexican Cooking