Preheat oven to 325 degrees.
Spray a large (13" x 18") baking sheet with nonstick spray.
In a separate bowl, whisk together the eggs, half-and-half, salt, and pepper.
Pour the eggs onto the baking sheet and sprinkle on the scallions.
Carefully transfer the baking sheet to the oven.
Cook for 15 - 18 minutes or until the eggs are set.
Remove the pan from the oven and let cool for 5 minutes.
While the eggs are cooking, warm the sausage according to the directions on the package.
Use a biscuit cutter or mason jar lid to make egg circles. I like the egg to fill the whole sandwich.
Assemble the sandwiches in this order: muffin or bagel bottom -> cheese -> sausage -> egg -> cheese scraps -> muffin or bagel top. I cut all the ingredients to fit inside the sandwich.