01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - Without separating the rolls, slice the whole block of Hawaiian rolls horizontally to create a top and bottom half.
03 - If using, whisk together Dijon mustard and mayonnaise. Spread evenly onto the cut sides of the rolls.
04 - Layer cheddar cheese evenly over the bottom half of the rolls. Place the top half over the cheese to reassemble.
05 - Place assembled rolls onto prepared baking sheet. Brush tops generously with melted butter. Sprinkle with garlic powder and dried parsley, if desired.
06 - Cover loosely with foil and bake for 10 minutes.
07 - Remove foil and bake an additional 5 minutes until the cheese is fully melted and tops are golden.
08 - Let rest 2 minutes, then cut apart into 12 mini sandwiches. Serve warm.