Combine pork butt, salt and 2 cups water in an 8-quart stockpot over high heat and bring to a boil. Turn down to a simmer and cook until pork is tender, 1 hour and 30 minutes.
Meanwhile, combine garlic cloves, serranos, cumin, black peppercorns, onion quarters, the chopped Anaheims and 2 cups water in a blender. Blend well until mixture is liquid, then slowly add cilantro. Continue to blend until mixture is completely liquid, then add mixture to stockpot (at whatever point the stockpot is at). Bring stockpot back to a boil, then, reduce heat back to a simmer.
Combine tomatillos and 1 cup water in blender and blend well until mixture becomes liquid, about 5 minutes. Add to stockpot and bring mixture to a boil again, then reduce the heat to medium.
Preheat the broiler.
Roast remaining whole Anaheim peppers in broiler, turning occasionally, until charred. Remove skin under cool running water and slice thin. Add to the stockpot in the last 30 minutes of cooking time.
Anaheim peppers can be roasted, cleaned and sliced ahead of time. Green Chili is excellent in burritos and tacos.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.