Sprinkle chicken with salt and pepper. In a Dutch oven, cook chicken over medium heat in 2 teaspoons oil for 4-6 minutes or until no longer pink; remove and set aside., In the same pan, saute onion in remaining oil until tender. Add garlic and ginger; cook 1 minute longer., Stir in the peas, tomatoes, sweet potato, broth, peanut butter, 1-1/4 teaspoons thyme and cayenne. Bring to a boil. Reduce heat; cover and simmer for 15-20 minutes or until potato is tender. Add chicken; heat through., Serve with rice if desired. Sprinkle with remaining thyme.