open up hamburger bun and kinda flatten with palm of your hand each half(dont forget to wash your hands before doing this LOL,continue with as many buns as you want to make,next spread a layer of mustard on each bun half. Next put a thin layer of hamburger on top of each mustard bun,make sure it covers the whole bun ,then put a layer of ketchup on top of the hamburger spread.
place all on cookie sheet,and turn on broiler on your oven,place close to broiler but not directly on the top rack. watch very carefully because it only takes a couple of minutes to broil,no time at all,they will be done when buns are a little crispy around edges. p.s,do not put a thick layer of hamburger on the bun a thin layer will do. Serve right away,hope you like them.