Grease a 9x13-inch baking dish with butter. Set the icing packets from the cinnamon rolls aside for later.
Cut each cinnamon roll into quarters and arrange the pieces evenly in the prepared baking dish.
In a medium bowl, whisk together eggs, heavy cream, vanilla extract, cinnamon, and maple syrup until smooth and well combined.
Pour the egg mixture evenly over the cinnamon roll pieces, making sure to coat them all. Gently press down so the rolls absorb some of the liquid.
Sprinkle chopped pecans over the top if using. Cover tightly with plastic wrap and refrigerate overnight (or at least 4 hours).
On Christmas morning, remove from refrigerator and let sit at room temperature for 20 minutes while you preheat the oven to 350°F (175°C).
Remove plastic wrap and bake uncovered for 30-35 minutes, until golden brown and the center is set.
Let cool for 5 minutes. Warm the reserved icing packets in the microwave for 10-15 seconds, then drizzle over the warm casserole. Serve immediately and watch it disappear!