Preheat the oven to 375 degrees.
Using a serrated knife, slice the rolls crosswise, leaving them all connected, to make a one giant top and one bottom. Work slowly to make the top and bottom as even in thickness as possible.
Spread the mayo and mustard (if using) over the bottom bun. Spread the fam over the top bun.
Layer the ham over the bottom rolls, then slice the Brie (to the best of your ability - it's sticky!) and layer that over the ham. Close the sandwich with the top num sheet.
Brush the butter over the top of the rolls. Shake the Everything Bagel Seasoning over the top.
Tent loosely with foil and bake for 10 minutes, then remove the foil and bake for 2 minutes more, or until cheese in melty. Let the sliders rest for a few minutes, then slice them apart and serve immediatly.
