Coat pressure cooker interior with nonstick spray and brown hens, onion, and garlic. Remove hens and tie a cheesecloth strip around the legs (to bind them to the bird so the meat does not fall off the bone).
Return wrapped hens to cooker, add broth, chili powder, ginger, and curry powder. Bring to high pressure and cook for 8 minutes, then reduce pressure quickly under cold water. Remove and unwrap hens. Reduce cooking liquid by 1/3, remove from heat, stir in yogurt and nuts to make sauce.