Heat 2 tbsp of the oil in a large skillet or wok. Season chicken with 1/4 tsp each of the salt and pepper. Add chicken to skillet and stir-fry 3 minutes. Remove to a bowl with a slotted spoon.
Add remaining tbsp oil to skillet. Stir in bok choy, red pepper and celery. Stir-fry 4 minutes, seasoning with remaining 1/2 tsp salt and 1/4 tsp pepper.
Meanwhile, mix chicken broth, soy sauce, cornstarch, sugar and hot sauce in a small bowl. Stir into skillet. Cook 1 minute and stir in sesame oil and sesame seeds. Serve with rice.