In a cup, mix the cornstarch with a little water to make a thickening agent, and set aside. Arrange the washed lettuce leaves in serving bowls, place 1/2 cup rice in the lettuce of each bowl and set aside. Heat wok or deep skillet over medium high heat. Add oil and garlic and stir fry garlic until golden brown. Add the chicken and stir until just cooked through. Break eggs into wok and stir well. Add the remaining ingredients in succession, stirring between each addition. When the broccoli is al dente, briefly stir the cornstarch mixture again and add to the center of the wok. Allow to thicken while stirring occasionally, about 2 minutes, then blend together with chicken and broccoli. Dish the contents of the wok over rice and lettuce leaves and serve.