Season chicken with salt & pepper. Heat cooker, add oil. Brown chicken a few pieces at a time. Sprinkle garlic, parsley, and oregano on chicken. Add onions, carrots, celery, tomatoes, salt, pepper and white wine. Close, cover securely. Place pressure regulator on vent pipe and cook 8 minutes with pressure regulator rocking slowly. Cool cooker all at once. Place chicken on warm platter. Stir tomato paste into sauce in cooker. Simmer until thickened. Pour over chicken.