Preheat your oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish. Using a long serrated bread knife, slice the entire 12-count slab of Hawaiian sweet rolls in half horizontally without pulling the individual rolls apart. Place the bottom slab into the baking dish.

In a large nonstick skillet over medium-high heat, cook the breakfast sausage for 5–6 minutes, breaking it into bite-sized crumbles until browned. Transfer to a plate with a slotted spoon and wipe the skillet clean.

Whisk together the 8 eggs, milk, salt, and black pepper. Pour into the warm skillet over medium-low heat with a pat of butter, gently folding with a silicone spatula for 2–3 minutes until just softly set into glossy curds (remove while still slightly underdone so they stay pillowy in the oven).

Arrange the 6 slices of sharp cheddar evenly over the bottom slab of Hawaiian rolls. Spoon the softly scrambled eggs and browned breakfast sausage on top, sprinkle with fresh chives, and cover with the 6 slices of Havarti or Colby Jack cheese. Place the top slab of rolls over the cheese.

In a small bowl, whisk together the melted butter, pure maple syrup, Dijon mustard, and garlic powder. Brush generously over the tops and sides of the rolls, then sprinkle with everything bagel seasoning.

Bake uncovered for 12–14 minutes until the tops are golden-toasted and the double layer of cheese is bubbling and melted. Slice between the rolls and serve warm!