-Take the husks off of 1 pound of tomatillos, wash them and cut them in half.
-In a blender, puree the following:
2 cups of chicken broth
1 bunch chopped cilantro, stems and all
2 jalapenos (optional)
4 whole cloves of garlic
-A fourth of the tomatillos.
-Set salsa verde aside.
-Cut a 4 pound pork shoulder into 1½ inch cubes.
-Brush heavy large pot with oil; heat over medium-high heat.
-Sprinkle pork with salt and pepper.
-Working in batches, add pork to pot; cook until browned, turning occasionally, about 4 minutes per batch.
-Using slotted spoon, transfer pork to bowl. Pour off all but 1 TBS fat from pot (add oil if needed).
-Chop up 2 leeks.
-Sprinkle with 1 TBS cumin seeds; cook until leek is soft and cumin is toasted, about 2 minutes.
-Add remaining tomatillos; cook until tender and browned in spots, stirring occasionally and reducing heat to medium if browning too quickly, about 8 minutes.
-Return pork and any juices to pot.
-Add two-thirds of the reserved salsa verde, 1 more cup broth and 2 tsp Mexican oregano (if you can find it).
-Cover; simmer over medium-low heat until pork is tender, about 2 hours.
-Serve with the remaining salsa verde, sour cream, warm tortillas and lime.