Green Pozole with Chicken

9 cups water (divided) 1 bay leaf 1 large white onion, halved lengthwise and thinly sliced (divided) 6 garlic cloves, chopped (divided) 1  teaspoon kosher salt, plus more to taste 3 lb. shredded chicken (original recipe called for thighs only, but I used a whole rotisserie) 1/2 cup hulled (green) pumpkin seeds 1 lb tomatillos, husked 1-2 fresh jalapeno chiles, quartered (with or without seeds) 3/4 cup chopped fresh cilantro 1 teaspoon dried oregano (preferably Mexican) 2 tablespoons vegetable oil 2 (15 oz) cans of white hominy, rinsed and drained sliced avocado and sour cream for garnish (if desired)   Toast pumpkin seeds in a small dry skillet over low heat, stirring occasionally, until puffed but not browned (seeds will pop as they puff), approximately 6-7 minutes. Meanwhile bring 7 cups of water, bay leaf, half of the onion, half of the garlic and 1 teaspoon salt to a boil, covered in a large stock pot, reduce heat and simmer 10 minutes.  Add shredded chicken and and simmer, uncovered, 15-20 minutes more.  Pour broth through a fine-mesh sieve into a large bowl, separating the chicken and onion and reserving the liquid.  Discard the bay leaf. While the chicken cooks, you can begin the sauce. Simmer tomatillos and remaining onion in remaining 2 cups of water until tender, approximately 10 minutes.  Add remaining garlic, jalapenos (depending on how spicy you want it), oregano, and 1/4 cup cilantro and puree with an immersion blender. In a large stock pot (I used the same one I pouched the chicken in), heat oil over moderately high heat.    Add the tomatillo puree (caution:  it might splatter and steam) and cook uncovered, stirring frequently until thickened, approximately 10 minutes.  Stir in the pumpkin seeds and 1-2 cups of the reserved broth and simmer 5 minutes.  Add in the shredded chicken, hominy and 3 more cups of the reserved broth.  Simmer partially covered, about 20 minutes. Stir in the remaining 1/2 cup cilantro and serve pozole in deep bowls