Beat the eggs and sugar with an electric beater or whisk for 2-3 minutes or until they are thick and pale. Add the milk, brandy and orange peel and stir the ingredients with a wooden spoon to blend them thoroughly.  Add the bread slices and let them soak for 4-5 minutes, turning them occasionally, until all of the liquid has been absorbed. Heat the butter on a griddle or large sauté pan over medium heat. When the butter has melted and looks foamy, cook the soaked bread slices for about 2 minutes per side or until lightly browned and crispy. Note: use two pans or cook half the slices at a time and keep cooked slices warm in a preheated 140-degree oven (repeat with the remaining slices).