Heat the oven to broil. Half the tomatillos and place them, along with 6 unpeeled garlic cloves, on a baking sheet and broil for 5-6 minutes
In a food processor or a blender add 1/2 of the pan of the roasted tomatillos, all of the roasted garlic cloves, cilantro, coarsely chopped green onions and peppers, and 1 cup chicken broth. Puree until chunky or smooth, depending on your preference. This is the salsa verde. Set aside.
Cut the pork into 1-2 inch pieces, removing some of the fat if it is really fatty. Heat 2 Tbsp olive oil (I used lief lard) in a dutch oven or a large skillet over high heat. Sprinkle pork with salt while waiting for the oil to heat (can sprinkle with pepper also if desired).
Add pork pieces to the heated pot, working in batches (don't crowd, a 5 lb pork butt will need to be divided into 3 batches). Cook until each side is browned, turning when golden brown. Remove pork pieces to a plate with a long slotted spoon or long tongs (the oil splatters) and cook the next batch.
When all pork is browned and removed from pot, lower the heat to medium and add the chopped onion to the leftover oil in the pot and cook about 5 minutes or until translucent.
Add the garlic and cumin seeds (or cumin powder) and cook about 1 minute until garlic is golden and cumin is toasted. Add remaining tomatillos and spices and cook until slightly browned, stirring occasionally (about 5 minutes).
Return pork to the pot, along with any juices on the plate. Add 2 cups of the salsa verde, 1 cup of broth, stir and bring to a gentle boil.
Reduce heat to low, cover pot and simmer over medium-low heat about 2 to 2 1/2 hours. Check occasionally and thin with chicken broth if needed.
Before serving, stir in remaining salsa verde and bring to a simmer. Accompaniments could include sour cream, cilantro sprigs, avocados and limes.