Remove the stems of the mushrooms. Wipe mushrooms with a damp paper towel. In a medium-sized bowl, combine the remaining ingredients.
Beat well with a wire whisk. Add the mushrooms and stir to coat them with the marinade. Let stand at room temperature for 3 hours or cover and refrigerate for 1 of 2 days.
When ready to serve, bring the mushrooms to room temperature, drain off the marinade, and put a toothpick into each mushroom.
Serve on a platter with a cluster of cherry tomatoes and pitted ripe olives in the center.
Makes about 6 servings.