Rinse mushrooms and pat dry, then cut off and chop the stems. Mix garlic, thyme, rosemary, and olive oil and drizzle this over the caps. Combine remaining ingredients with chopped stems in a small saucepan. Simmer for 5 minutes. Baste caps with sauce, and grill (or broil) for 2 to 3 minutes per side. Serve with rice, with sauce on the side.