01 - Preheat oven to 175°C. Grease a 23x33 cm baking dish with nonstick spray or butter.
02 - In a large skillet over medium heat, cook the beef sausage and onion (if using), breaking it into small pieces, until browned and fully cooked, about 6 to 8 minutes. Drain excess fat and stir in black pepper. Set aside.
03 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
04 - In a separate bowl, whisk eggs, buttermilk, melted butter, and vanilla extract until uniform.
05 - Gently mix the wet ingredients into the dry ingredients until just combined. Batter may remain slightly lumpy—do not overmix.
06 - Evenly pour half of the pancake batter into the prepared baking dish.
07 - Sprinkle the cooked sausage mixture evenly over the batter. Drizzle 80 milliliters maple syrup over the sausage.
08 - Spread the remaining pancake batter over the sausage layer, covering it completely.
09 - Sprinkle shredded cheddar cheese evenly over the surface.
10 - Bake for 35 to 40 minutes, or until golden brown and a toothpick inserted in the center comes out clean.
11 - Allow casserole to cool for 5 to 10 minutes before slicing. Serve warm with additional maple syrup if desired.