Start by preheating a non-stick skillet or griddle over medium heat and lightly greasing it with cooking spray or butter. In a medium bowl, mix the flour, baking powder, salt, and sugar. In a separate bowl, whisk together the milk, egg, maple syrup, and melted butter. Combine the wet and dry ingredients, stirring until just mixed. Be careful not to overmix to avoid dense pancakes. Drop tablespoon-sized amounts of batter onto the skillet to form mini pancakes, and cook for about 1 to 2 minutes until bubbles form on top. Flip and cook the other side for another 1 to 2 minutes until golden brown. While the second side cooks, place a small spoonful of sausage and cheese onto half of the pancakes, then top each with another mini pancake to form a sandwich. Remove from heat, let them cool slightly, and serve warm with extra maple syrup if desired.