01 - Heat a large nonstick skillet or griddle over medium heat until evenly warmed.
02 - Combine honey mustard and mayonnaise in a small mixing bowl, stirring until smooth and fully incorporated.
03 - Open each Hawaiian roll and spread a thin layer of the honey mustard mixture on the cut sides of both halves. Place one half-slice of cheddar cheese on each bottom bun. Add ham half-slice if desired, then cover with the bun tops.
04 - Spread softened butter evenly over the outside top and bottom surfaces of each assembled mini sandwich.
05 - Arrange sandwiches in the preheated skillet, pressing gently with a spatula. Cook for 2 to 3 minutes per side until bread achieves golden-brown color and cheese melts completely.
06 - Remove from heat and immediately sprinkle with poppy seeds and chives if using. Serve warm while cheese remains melted.