Breaded Butterflied P

I didn’t have any Panko on hand today, so I just used the Pecorino Romano bread crumbs. 8 ounces button mushrooms 1 egg white 1/4 cup grated Pecorino Romano or Parmesan cheese 1/4 cup Italian seasoned Panko breadcrumbs 1/4 teaspoon garlic powder salt and pepper, (about 1/4 teaspoon each)