Grease the bottom and sides of a 9 × 12-inch baking pan with butter. Arrange bread slices in the pan. In a bowl beat eggs, milk, sugar, syrup, vanilla, and salt. Pour the mixture over the bread. Turn bread slices to coat. Cover with foil or plastic wrap and refrigerate overnight. The next morning preheat oven to 375 degrees. Bake French toast uncovered for 15 minutes. Turn bread slices over and continue baking until golden brown, about 10 minutes.
