01 - Grease a 9x13-inch baking dish generously with cooking spray or softened butter, ensuring even coverage on all surfaces.
02 - Arrange the pancakes in the prepared baking dish in a single layer, overlapping them 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, salt, black pepper, cinnamon, and vanilla extract until fully combined and smooth.
04 - Scatter the desired add-ins — sausage or bacon crumbles, shredded cheddar cheese, and/or fresh fruit — evenly across the pancake layer.
05 - Slowly and carefully pour the egg custard mixture over the pancakes and fillings, tilting the dish gently to ensure even coverage throughout.
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 while the oven comes to temperature.
08 - Drizzle the maple syrup evenly over the top of the casserole. Bake uncovered for 40 to 45 minutes until the top is golden brown, the center is puffed and set, and a knife inserted in the middle comes out clean.
09 - Allow the casserole to rest for 10 minutes before slicing into portions. Dust with powdered sugar and garnish with fresh fruit if desired. Serve warm.