1 1/2  pounds tomatillos, peeled and washed
3 serrano chilies, washed, seeds removed and deveined 
1/2 onion, chopped
4 cloves garlic, roughly chopped
1/4 cup cilantro, washed, stems removed, leaves  roughly chopped
1 teaspoon salt, to taste

Remove the stems of and quarter the tomatillos; toss into the bowl of a food processer. Roughly chop chilies and add to the bowl and blend until the mixture reaches a thick, salsa consistency. Add onion, garlic, cilantro and salt and blend again to incorporate. Test for heat and salt and adjust to taste. Serve at room temperature.