01 - Heat a large nonstick skillet or griddle over medium heat until evenly hot.
02 - Whisk together honey mustard and mayonnaise in a small bowl until smooth and well combined.
03 - Open each Hawaiian roll and spread a thin layer of honey mustard mixture on cut sides of both halves. Place half a cheddar slice on each bottom bun, add ham half if desired, and close with top bun.
04 - Spread softened butter generously over the outside tops and bottoms of each assembled roll.
05 - Arrange mini sandwiches in the preheated skillet, pressing gently with spatula. Cook for 2–3 minutes per side until golden brown and cheese is completely melted.
06 - Sprinkle with poppy seeds and fresh chives immediately after removing from heat, if using.
07 - Transfer to a serving platter and serve warm while cheese is still melted.