In a medium bowl, whisk together the eggs, whole milk, salt, and black pepper until fully combined.
Heat the unsalted butter in a non-stick skillet over medium heat until melted and foamy.
Pour the egg mixture into the skillet and cook, gently stirring with a spatula, until the eggs are softly scrambled and just set, about 3 to 4 minutes. Remove from heat.
In a separate skillet, cook the turkey sausage patties over medium heat until browned and cooked through, about 4 minutes per side. Remove from heat and drain on paper towels.
Slice each croissant in half horizontally, being careful not to cut all the way through, creating a hinge.
Place one slice of cheddar cheese on the bottom half of each croissant.
Divide the scrambled eggs evenly among the croissants, placing them on top of the cheese.
Top the eggs with one turkey sausage patty each.
Close the croissants over the filling.
To freeze, wrap each sandwich tightly in plastic wrap, then place all wrapped sandwiches in a large freezer-safe zip-top bag. Label with date.
To reheat, unwrap the sandwich and microwave on a microwave-safe plate for 1 to 2 minutes or until heated through. Alternatively, reheat in a 350°F oven for 15 to 20 minutes, wrapped in foil.