Open (2) 17.5-ounce cans refrigerated Grands cinnamon rolls and set both containers of icing aside. Cut each cinnamon roll into 6 equal pieces and arrange the pieces evenly in the prepared baking dish.

In a medium mixing bowl, whisk 3 large eggs until they are blended. Add ⅓ cup heavy cream, 3 tablespoons pure maple syrup, and 1 teaspoon ground cinnamon, then whisk until smooth and evenly combined.

Slowly pour the egg mixture over the cinnamon roll pieces. Gently turn the pieces with a silicone spatula to lightly coat them and distribute the egg mixture throughout the baking dish without pressing or packing down the dough.

For the overnight method, cover the baking dish tightly and refrigerate for 8 to 12 hours. Then, when you're ready to bake, remove the casserole from the refrigerator and preheat the oven to 350°F. For the same-day method, bake once the oven is fully preheated.

Bake uncovered at 350°F for 30 to 35 minutes for the same-day method or 35 to 40 minutes after overnight refrigeration. The casserole is ready when the top is golden brown and puffed, the center is set, and a cinnamon roll piece from the center is baked through without wet or gummy dough. If the top browns too much before the center is done, loosely cover the baking dish with aluminum foil for the remaining baking time.

Remove the casserole from the oven and let it rest for 10 minutes. Place the reserved icing from both cans in a microwave-safe bowl and warm for about 10 seconds, just until it is easy to drizzle. Drizzle all of the icing evenly over the warm casserole.