Preheat oven to 350 degrees F.

Spray the bottom of a casserole dish with cooking spray. Cut sliders in half and place the bottoms in the casserole dish.

In a bowl, mix together softened butter, mustard and onions then spread over the bottom buns. Save some mixture for the top buns.

Place 2 layers of ham over top the buns overlapping the pieces of ham.

Cut the swiss cheese pieces in half and place them on top of the ham.

Spread the butter, mustard and onion mixture on the top buns and place on top of the ham and cheese.

Brush a thin layer of the mixture over top the buns and sprinkle with Italian seasoning. Cover with foil and bake for 20 minutes. 

When finished cooking, cut the sliders apart with a knife. Serve warm and enjoy!