Hot Roast Beef & Cheese Sandwiches (for a crowd!)

hamburger buns

thinly sliced roast beef

slices provolone cheese

For the sauce!

freshly minced onion (grate onion on a couple of paper towels and squeeze out the excess moisture)

mayonnaise

spicy brown mustard

prepared horseradish

poppy seeds

Worcestershire sauce

garlic powder