PLACE pumpkin seeds in large skillet; cook and stir on medium heat 2 min. or until lightly toasted. Spread onto paper towel; cool.
MEANWHILE, place chicken in large skillet. Add broth; cover. Cook on medium heat 15 min. or until chicken is cooked through, stirring occasionally. Remove chicken from skillet, reserving 3 cups of the broth; cover chicken to keep warm.
POUR half of the reserved broth into blender. Add half each of the pumpkin seeds, tomatillos, cilantro, onions and cracker crumbs; cover. Blend until smooth; pour into skillet. Repeat. Cook on medium-high heat 5 min. or until heated through, stirring occasionally. Reduce heat to low. Add sour cream; stir until well blended. Return chicken to skillet; cover. Simmer 10 min. or until heated through.