Preheat an oven to 200°C. Cut the panettone into 5 or 6 vertical slices, each 1 inch thick, then cut all but the end slices in half. Set aside. In a bowl, whisk the eggs until just blended, then whisk in the milk,orange zest, orange juice, Cointreau, sugar and cinnamon. Pour the mixture into a large, shallow baking dish. Place half of the panettone slices in the mixture and soak for about 10 seconds per side. Set a large sauté pan or grill pan over medium heat and brush with butter. When the butter foams, add some of the soaked bread slices, taking care not to crowd them. Cook, turning once, until lightly browned, 3 to 5 minutes per side. Turn the slices over again and cook them until browned to your taste, 2 to 3 minutes more. Using a slotted spatula, transfer the panettone to a platter and keep warm in the oven. Cook the remaining soaked slices, then soak and cook the rest of the panettone. Serve immediately with Fabbri Amarena Cherries and whipped cream.