Preheat the oven to 350°F (175°C).
In a medium bowl, whisk together the eggs, milk, salt, and black pepper until fully combined.
Heat a non-stick skillet over medium heat and add the unsalted butter.
Pour the egg mixture into the skillet and cook, stirring gently, until the eggs are softly scrambled and cooked through, about 3-4 minutes. Remove from heat.
In a separate skillet, cook the turkey sausage patties over medium heat until browned and cooked through, about 4-5 minutes per side. Remove from heat.
Slice each croissant in half horizontally.
Assemble each sandwich by layering one cooked turkey sausage patty on the bottom half of the croissant, followed by a slice of cheddar cheese, then a portion of scrambled eggs. Top with the croissant top half.
Wrap each sandwich tightly in plastic wrap, then in aluminum foil for extra protection.
Place the wrapped sandwiches in a freezer-safe zip-top bag or airtight container and freeze for up to 3 months.
To reheat, remove the foil and plastic wrap, wrap the sandwich in a paper towel, and microwave on high for 1-2 minutes until heated through. Alternatively, reheat in a 350°F (175°C) oven for 15-20 minutes if frozen solid.