01 - Grease a 9x13-inch baking dish generously with cooking spray or softened butter, ensuring all surfaces are coated to prevent sticking.
02 - Arrange the pancakes in the prepared baking dish in a single layer, overlapping slightly to cover the entire bottom. Brush the tops evenly with the melted butter.
03 - In a medium mixing bowl, whisk together the eggs, whole milk, heavy cream, kosher salt, black pepper, ground cinnamon, and vanilla extract until fully combined and smooth.
04 - Scatter the desired add-ins — crumbled sausage or bacon, shredded cheddar cheese, and/or fresh berries — evenly across the pancake layer.
05 - Slowly pour the egg custard mixture over the pancakes and add-ins, tilting the dish gently to ensure even coating throughout. Press down lightly on any dry edges to submerge them.
06 - Cover the dish tightly with plastic wrap or aluminum foil and refrigerate for a minimum of 4 hours, preferably overnight, to allow the custard to fully soak into the pancakes.
07 - Preheat the oven to 350°F. Remove the baking dish from the refrigerator, uncover it, and let it stand at room temperature for 15 to 20 minutes while the oven comes to temperature.
08 - Drizzle 2 tablespoons of pure maple syrup evenly over the top of the casserole before baking.
09 - Bake uncovered for 40 to 45 minutes, or until the top is golden brown and puffed, and the center is fully set with no visible liquid when gently pressed.
10 - Remove from the oven and let rest for 10 minutes before slicing into portions. Dust with powdered sugar and garnish with fresh berries or sliced bananas if desired. Serve warm with additional maple syrup or whipped cream on the side.