Cut eight 1-inch slices diagonally from a loaf of day-old French (not Italian) bread with a serrated knife and reserve the remaining bread for another use. Arrange the slices on a baking sheet and let them stand in a warm dry place, turning them several times, for 12 hours, or until they are completely dry.

In a bowl beat 4 large eggs with 3 Tbsp. Sugar and a pinch of salt; add well combined. Transfer the bread slices to a baking dish just large enough to hold them in one layer; add the egg mixture, and let the slices soak, turning them carefully once or twice, for 30 to 45 minutes, or until they are soft and have absorbed most of the liquid.

Heat a large griddle over moderately high heat until it is hot and brush it with melted unsalted butter. Transfer bread slices with a slotted spatula to the griddle in batches and cook them, turning them once and brushing the griddle as necessary with melted unsalted butter, for 6 to 8 minutes, or until they are golden brown and slightly puffed. Transfer the toast as it is cooked to an oven-proof platter and keep it warm in a preheated very slow oven (150 F). Spoon 1 Tbsp. Orange sauce over each piece of French Toast and transfer remaining sauce to a heated sauceboat.