Preheat the oven to 375°. Butter or spray a 7" x 11" baking dish.
Cut the bread into ¾" pieces. There is no need to trim the crusts unless the bottom crust is quite browned, in which case trim the dark part away before cubing the loaf. Set aside.
In a large mixing bowl, whisk together eggs, cream (or lesser amount of milk), vanilla, salt and th optional orange zest and/or cinnamon, if using, until the ingredients ar thoroughly combined and bubbly. Fold in the bread cubes turn over and over until th read is thoroughly soaked in the custard mixture. Set aside 15 minutes, stirring a couple of times, until all of the custard has been absorbed into the bread. If making ahead, cover tightly and place in the bread/custard mixture in the refrigerator until 30 minutes before serving.
Just before baking gently stir the frozen or fresh berries into the bread mixture. If using frozen berries, do not thaw in advance. Tip the mixture into the prepared baking dish. Sprinkle the top with nuts and sugar. Place in the oven and bake until golden brown on top, 18-22 minutes.
Remove from the oven and allow to cool for five minutes before cutting into squares.