Preheat your oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish.
In a skillet over medium heat, cook the breakfast sausage links until browned and cooked through, about 8-10 minutes. Remove from heat and slice into bite-sized pieces.
In a large mixing bowl, whisk together the eggs, milk, vanilla extract, and brown sugar until well combined.
Add the pancake mix, baking powder, cinnamon, and salt to the egg mixture. Stir until just combined (do not overmix; it's okay if there are a few lumps).
Fold in the cooked sausage pieces gently into the pancake batter.
Pour the pancake-sausage mixture evenly into the greased baking dish.
Bake in the preheated oven for 30-35 minutes or until the top is golden brown and a toothpick inserted into the center comes out clean.
Let the casserole cool for a few minutes before slicing.
Serve warm, drizzled with maple syrup and topped with fresh berries if desired.
Notes
Serve warm with maple syrup and fresh berries for added flavor.