Begin by blending the garlic with the cilantro roots in a mortar or spice grinder and then scrape into a bowl.
Next, put the mushrooms in a food processor and pulse briefly until they are finely chopped. Add the garlic mixture, and then stir in the curry paste, egg, sauces, sugar, and lime leaves.
Now, after placing the pepper halves in a steamer basket, spoon the mixture loosely into the peppers. Bring the water in the steamer to a boil, then lower the heat to simmer, and steam the peppers for 15 minutes, or until the flesh is tender.