02In a saucepan, boil the tomatillos, garlic, jalapenos, serrano and half of the onions in 2 cups water until the mixture floats to the top of the saucepan, about 30 minutes. Strain out the pulp and reserve the liquid.03In a food processor, blend the pulp with the remaining onions, the cilantro, salt and 3/4 cup of the reserved liquid.