Bone your chicken reserving all the meat and discarding the bones. Reserve.
Toast Pumpkin seeds in a 350F oven until seeds begin popping, about 10 minutes. Allow seeds to cool and grind until fine with a spice grinder. Combine seeds with 1/2 cup of stock and set aside.
In a sauce pot, heat lard until smoking. Add seed paste, fry for about 3 minutes. Scraping bottom of pan to prevent burning.
Add 4 cups of stock and stir well. Add chicken meat and cook at simmer for about 15 minutes.
Meanwhile, in a blender combine jalapenos, tomatillos, epazote, cilantro, salt, and remaining stock.Blend until smooth.
Stir blended mix into liquid and stew on low heat until the chicken is tender for about 35 minutes. Shred chicken back into liquid. Adjust seasoning to taste, if needed. Serve on tortillas.