Wash and dry mushrooms, remove stems and clean out the gills. Save for another use. (I use mine for pizza topping or in scrambled eggs.)
Mince or pulse tomatoes in food processor until fine.
Mix ingredients. Stuff mushrooms, don't pack them too hard or they will break the mushrooms, but you can stack them up since the stuffing is not very mushy.
Place on ungreased baking sheet. Put them gently into the oven or they will all fall over and cook on thier sides. Cook for 25 minutes or until they are firm to the touch. Makes about 15 bite size appetizers.