Bring a medium-size saucepan of water to a boil then blanch the kohlrabi, carrot, and bitter melon separately for 2 minutes each. Blanch the green beans for 1 minute. Immediately transfer the vegetables to an ice bath to stop the cooking process and to keep the vegetables crisp.
Place a clay pot on high heat. Add the vegetable oil and fry the garlic until fragrant. Now add the sugar, soy sauce, sesame oil, pepper, and water. Bring the mixture to the boil then add the drained vegetables, mushrooms, and tofu. Stir well to incorporate and allow to simmer for 5 minutes.
Garnish the dish with fresh coriander (cilantro) and serve with steamed jasmine rice.
If using a clay pot, soak the pot in cold water 24 hours before using.