How to Make It
In a blender, combine the onion, Asian pear, kiwi, garlic, ginger, both sugars, sesame oil, soy sauce and water and puree until smooth.
Arrange the mushroom caps in a shallow baking dish and pour the marinade on top. Turn the mushrooms to coat them completely with the marinade. Let the mushrooms stand at room temperature for at least 30 minutes or refrigerate for up to 24 hours.
Light a grill. Lift the mushrooms from the marinade, shaking off the excess. Grill over moderately high heat, turning occasionally, until tender, about 12 minutes.
Variation The marinade is great for thinly sliced flanken-style short ribs or steak.