Preheat oven to 350 degrees. Spray an 9 x 13 inch baking dish with nonstick cooking spray. Leaving the dinner rolls intact, slice them open with a serrated knife so that you have one solid top and bottom. Place the bottom half in the baking dish. Spread dijon mustard on the top and bottom.

Place half of the sliced cheese on the bottom half followed by the sliced ham, sliced turkey, and remaining cheese. Replace the top half of the rolls.

In a small bowl, whisk the egg and slow drizzle in the melted butter while whisking. Brush the mixture on top of the rolls.

Cover with loosely with foil (don't let it touch the tops of the rolls to avoid sticking - use toothpicks if necessary to "lift" the foil).

Bake at 350 degrees for 15 minutes. Remove foil and continue to bake for another 10 minutes or until tops are golden brown.

Cool slightly, then cut apart with with a serrated knife. Sprinkle the top powdered sugar. Serve hot with berry jam on the side. Serves 4 as a main dish or 12 as an appetizer.