Roast Beef Dip Sandwhich

What do you do with left over Roast Beef? Make a beef dip, of course!

There isn't really a recipe for this one. It's a "throw together" leftovers meal. I also cheated and used a packet au jus gravy mix from the grocery store, although there are several recipes online if you'd prefer to make an au jus from scratch.

1 tablespoon butter
3 button mushrooms, sliced thin
1/4 small onion, sliced thin
Left over roast beef, sliced thin
slices of mozzarella or provolone cheese
crusty hoagie style buns
horseradish mustard (optional)

1. Melt butter in a saute pan. Add onion and mushroom and cook until onions are translucent and mushrooms are browned. Add roast beef slices to pan just to warm through slightly.

2. While onions and mushrooms are cooking, slice open and toast hoagie bun. Once toasted, butter the bun and dress with horseradish mustard or any condiment of your choice.

3. Arrange sliced beef evenly over the bottom hoagie bun. Top with cheese slices and then layer onion and mushroom mixture on top. Replace top bun. Slice in half and serve with a cup of au jus for dipping.