Heat oven to 375°F. In skillet, cook beef over medium-high heat 5 to 7 minutes.

Once beef is browned stir in ketchup, mustard, and onion.

In medium bowl, stir bisquick mix and boiling water until dough forms. DIvide dough into 5 equal pieces. Place dough pieces on surface sprinkled with Bisquick mix; roll the dough on the sprinkled surface. Roll each piece into 6 inch round and 1/4 inch thick.

Spoon beef mixture onto one side of each dough round to within 1/2 inch edges. Top beef on each round with cheese. Fold dough in half, covering filling. Press edges with fork to seal. On ungreased cookie sheet, place calzones.

Brush calzones with egg. Sprinkle with sesame seed. Bake 15 to 20 minutes or until golden brown.