Meanwhile preheat the broiler on high.
Place the tomatillos, ½ onion (chopped), 2 garlic cloves, and 2-3 serrano chiles on a sheet pan.
Note: if you like it spicy, use 4 to 5 serrano chiles.
Drizzle 1 tablespoon of oil over all the ingredients and mix well.
Add salt over everything.
Place the sheet pan inside the oven.
Broil for 4-5 minutes until the tomatillos are black and charred.
Add all the tomatillos and cilantro into a blender.
Blend until smooth.
If there is excess fat, remove the seared pork from the pot.
Drain any excess fat.
Place the remaining 1/2 onion chopped and 1 finely minced garlic into the pot.
Stir and cook for 1 minute.
Return the pork to the pot.
Add the salsa verde from the blender.
Add 1 cup of chicken broth to the blender to get any remaining salsa verde.
Add the liquid from the blender and remaining chicken broth to the pot.
Stir to combine.
Cover with a lid.
Cook for 1 hour on low.
Taste for salt.Note: If using potatoes, add 30 minutes before turning off the heat.
Serve with Mexican rice and beans.