For the sauce, combine all ingredients in a small bowl and set aside.
For stir-fry, wash, peel and cut carrots and sweet potato into 1/4 inch stick shaped.
Tear mushrooms, if using, along gill lines into evenly sized strips.
Cut asparagus into snow-pea-size lengths.
Place a Wok or large skillet over med-hi heat and heat oil until it shimmers. Working in batches, if necessary, stir-fry carrot and sweet potato sticks for 2 minutes, until slightly dark and fragrant. Add asparagus and mushrooms, if using, and cook for 2 minutes.
Increase heat to high and add snow peas and the sauce (and the first batch of stir-fried vegetables, if necessary).
Cook, stirring constantly, for a minute or two until sauce comes to a boil and vegetables are well coated.
(If using shrimp, add them at this point and toss to heat through).
Season with salt and black pepper to taste.
(Discard garlic from sauce, if desired).
Divide among individual plates and sprinkle w/chopped parsley.