Preheat your oven to 375°F (190°C). Lightly grease a standard 9x13 inch baking dish with the tablespoon of butter or cooking spray. Open the canned cinnamon rolls and set the included icing packets aside for later use.

Place each cinnamon roll flat on a cutting board and cut each roll into four equal pieces (quarter them). Scatter the cut pieces evenly across the bottom of the prepared 9x13 inch baking dish.

In a large bowl, whisk together the 6 large eggs, 1/2 cup whole milk, 1/4 cup heavy cream, 1 teaspoon vanilla extract, and 1/2 teaspoon ground cinnamon. Whisk until the mixture is uniform and slightly frothy.

Carefully pour the liquid custard mixture evenly over the scattered cinnamon roll pieces in the baking dish, ensuring all pieces are thoroughly coated. Allow the bake to sit undisturbed for 5 to 10 minutes to allow the cinnamon rolls to fully absorb the liquid.

Place the baking dish into the preheated 375°F (190°C) oven. Bake for 28 to 32 minutes, or until the top is golden brown, the center is set, and a knife inserted near the center comes out clean.

Remove the French toast bake from the oven and place it on a wire rack. Prepare the reserved icing packets by warming them slightly in a bowl of warm water or microwaving the unsealed icing for 5-10 seconds to loosen the consistency.

Snip the corner of the icing packets and generously drizzle all the icing over the warm French toast bake. Serve immediately.