Beef-Broccoli Strudel with Mozzarella

1 pound ground beef
1 onion chopped
1 10 oz pkg frozen chopped broccoli thawed, drained
4 ounces Mozzarella cheese shredded
1/2 cup sour cream
1/4 cup dry bread crumbs
8 ounces phyllo dough thawed
1/2 cup melted butter

Brown ground beef and onion in skillet, stirring until ground beef is crumbly; drain. Mix in broccoli, cheese, sour cream and bread crumbs. Cook until heated through and cheese is melted.
Place sheet of phyllo on waxed paper, brush with butter. Repeat with remaining dough, layering sheets. Spoon ground beef mixture evenly on half the dough. Roll up from ground beef side as for jelly roll. Place seam side down on baking sheet; brush with remaining butter.
Bake at 350F for 45 minutes or until golden brown.