Preheat the oven to 350°F (175°C).
Form the ground sausage into 6 equal-sized patties.
Heat a skillet over medium heat and cook the sausage patties for about 4-5 minutes per side, until fully cooked and browned. Remove from skillet and set aside.
In the same skillet, reduce heat to low and add butter.
Spray a round 6-inch wide cooking ring or use a small bowl to shape the eggs.
Crack one egg into the cooking ring and cook on low heat until the white is set and yolk is cooked through, about 3-4 minutes. Season with salt and pepper. Repeat for all eggs.
Remove eggs from skillet and set aside.
Slice the croissants in half horizontally and toast lightly in the oven for 3-4 minutes until slightly crisp.
Assemble each sandwich by layering one sausage patty, one cooked egg, and one slice of cheddar cheese on the bottom half of each croissant.
Place the top half of the croissant over the cheese.
Wrap each sandwich tightly in plastic wrap and then in aluminum foil.
To freeze: Place wrapped sandwiches in a freezer-safe bag or container and freeze for up to 1 month.
To reheat: Remove foil and plastic wrap. Wrap sandwich in a paper towel and microwave on high for 1-2 minutes until heated through, or bake in a preheated 350°F (175°C) oven for 15-20 minutes until hot.