In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In a separate bowl, whisk the buttermilk, egg, vanilla extract, and melted butter until combined.
Pour the wet ingredients into the dry ingredients and stir gently until just combined; do not overmix. The batter will be slightly lumpy.
Heat a griddle or large non-stick skillet over medium heat and lightly grease with butter or cooking spray.
Pour about 2 tablespoons of batter per pancake onto the griddle to form small, round pancakes approximately 3 inches in diameter.
Cook pancakes for 2-3 minutes until bubbles form on the surface and edges look set, then flip and cook for another 1-2 minutes until golden brown. Transfer to a plate and repeat with remaining batter.
In the same skillet, cook the sausage patties over medium heat until browned and cooked through, about 3-4 minutes per side. Remove and drain on paper towels.
To assemble the McGriddles, place one pancake on a clean surface, top with a cooked sausage patty, then a slice of American cheese, and finally another pancake to form a sandwich.
Allow sandwiches to cool completely before wrapping each tightly in plastic wrap.
Place wrapped sandwiches in a freezer-safe zip-top bag or airtight container and freeze for up to 1 month.
To reheat, unwrap a frozen sandwich and microwave on high for 60-90 seconds or until heated through. Alternatively, reheat in a toaster oven at 350°F for 10-12 minutes.