Slice ciabatta rolls lengthwise.
Divide ham & cheese evenly among rolls.
Prepare honey mustard by combining mayo, honey, dried mustard, and 1 tsp. poppy seeds.
Divide honey mustard evenly among sandwiches.
Combine 1 Tbsp. melted butter and 1/4 tsp. poppy seeds; brush on top of sandwiches.
Bake at 350 degrees for 15-20 minutes.