Pound garlic and shallots in mortar and pestle until fine. Put in bowl, add coriander powder, sliced green onion and add the flours. Pour in water gradually while stirring to make a smooth batter. Season with salt and pepper.
Heat wok with oil until hot. Dip each slice of the tempeh into the batter and lower in hot oil. Deep fry until batter becomes crispy and sets yet the colour is still pale and not dark. Remove from oil and drain on paper towel. Serve with dipping sauce.