In a high walled saute pan over medium heat, add butter. Once melted add onions and let saute for about 3 minutes. Then add seasonings, Worcestershire and one cup of broth. Let come just to a bubble while stirring often.
Preheat oven to 425degF.
Reduce heat of au jus to low and let continue to simmer. Stir occasionally.
Cut each roll in half and place the bottoms on a parchment paper covered baking sheet. Pile 2-3 slices of roast beef on to each (should fold up so there isn't too much overhang). Place a half slice of cheese on top of each.
Once oven is hot, place baking sheet in for 8-10 minutes. You want the cheese just melted.
When you remove the sheet, immediately place the top buns on each. Cut each sandwich in half.
Spoon au jus into ramekins and serve right away.
Keyword au jus, french dip, roast beef, Swiss Cheese