Broccoli gratin with Toasted Parmesan-Dijon Breadcrumbs
4 tablespoons (1/2 stick) butter 1/3 cup minced onion 2 large garlic cloves, minced 1/2 teaspoon dry mustard 4 tablespoons Dijon mustard 2 1/2 cups fresh breadcrumbs made from crustless sourdough bread 1 cup (packed) grated Parmesan cheese (about 3 Read on!