Whisk cornstarch into water in a bowl. Put chicken stock, soy sauce, crushed garlic, and bay leaves in a small pot and bring to a boil. The moment stock boils, whisk in cornstarch mixture. Return to a boil. Reduce heat to low and lightly simmer for about three minutes, or until volume has reduced slightly. Turn off heat but keep warm.
Set up bamboo steamer with two trays over pot of boiling water. Arrange broccoli evenly in first tray. Cover with steamer lid. Steam broccoli for two minutes, so that it begins to cook and broccoli and chicken will be ready at the same time.
Arrange chicken in second tray. Place over broccoli and steam for four to six minutes, or until chicken is fully cooked and no pink color remains. Combine chicken and broccoli on a platter, season with salt and pepper if desired, and drizzle with garlic soy sauce or light soy sauce. Serve immediately with rice.