Cut cheese into 1/2-in. slices; cut each slice in half diagonally. In a shallow bowl, combine bread crumbs and red pepper flakes if desired. In another bowl, beat egg. Dip cheese triangles into egg, then in crumb mixture.
Place on a greased baking sheet. Broil 4 in. from the heat for 2-3 minutes or until browned and cheese begins to melt. Serve warm with pizza sauce for dipping.