1. Preheat oven to 375 degrees F. Line a cookie sheet with foil, and place mushrooms on it. Set aside.
2. In blender, combine grated garlic, onion, 1 sprig rosemary (remove stem), red wine vinegar and olive oil. Blend until mixed, but not smooth. You should be able to see pieces of onion in the mixture.
3. Spread mixture over the mushrooms and use your hands to evenly coat. Sprinkle salt and pepper; place the other rosemary sprig across mushrooms. Fold foil over mushrooms to create an envelope and poke a few holes in the top to allow steam to escape.
4. Bake for 35 to 40 minutes. Remove rosemary sprig before serving.
This dish would be great as a side to rice or placed in pasta or served as an appetizer. This dish has lots of flavor. If you don’t like sharp tastes, lessen amount of garlic and/or onion. You can use whatever mushrooms you like; simply adjust baking time on size of mushrooms.
Source of recipe: I made this recipe up while cleaning out the fridge.