In a large pot set to medium heat sauté the mushrooms in 1 tbsp. of oil until golden brown about 6-8 min.
While the mushrooms are cooking, toast the pumpkin seeds lightly in a small sauté pan over medium heat. Remove from pan and set aside.
Remove the mushrooms from the pot, and add the onions. Turn heat down to medium-low and sweat onions until tender and transparent about 4-5 minutes.
Add garlic and cook for two more minutes. Return the mushrooms to the pot. Pour in the vegetable stock and hominy and simmer softly until you are ready to add the sauce.
Turn oven broiler on to HI setting.
Place the poblano peppers, serrano peppers, and tomatillos on a sheet tray lined with foil. Place under the broiler for 3 minutes or until the peppers have begun to get dark spots. Flip the peppers and tomatillos over and let cook for 3 more minutes. Remove from the oven and set aside.
Place the poblano peppers in bowl and cover with plastic wrap. Let sit 5 minutes.
Peel poblano peppers and remove the stems and seeds.
Place the poblano peppers, serrano peppers, pumpkin seeds, tomatillos, greens, epazote, cilantro, cumin, and oregano in a blender and process until smooth.
10. Strain the sauce into a medium sauce pot set to medium-low heat. Let sauce simmer for 5-6 minutes or until it changes to a darker green color.
11. Pour sauce into the pot with the mushrooms and hominy and bring to a simmer. Simmer for 8-10 minutes, and season with salt and pepper.
12. Serve with garnishes.