The filling: equal parts seasoned bread crumbs & parmesan, plus chopped parsley and minced garlic. Add just enough olive oil to bind everything together.
Clean mushrooms, remove stems, and spoon filling into the hollow part. Arrange on an oiled baking sheet, drizzle with olive oil, and bake at 400 for about 15 minutes (until breadcrumbs are golden).
Lean, ground angus beef, with a minced garlic clove mixed in, and seasoned with salt & pepper. Cooked in a very lightly oiled pan on the stove, until the outside has a nice crust, and the inside is slightly on the rare side of medium. The bun is a toasted potato roll—each side has a light coating of mayo, and a dusting of freshly ground black pepper—and the burger is topped with a paper-thin slice of tomato.