Mix together the granulated sugar and two teaspoons of ground cinnamon. Sprinkle it over the diced apples and stir to coat. Set aside.
In a separate bowl, whisk together eggs, half-n-half, apple sauce, caramel syrup, brown sugar, vanilla extract, two teaspoons of cinnamon, nutmeg, and salt.
Make the bottom layer in a greased slow cooker or casserole dish by spreading four cups of the cubed bread on the bottom. Sprinkle with one cup of the diced apples and a quarter cup of the chopped walnuts. Pour half of the egg mixture over the bottom layer.
Make the top layer by adding the remaining ingredients in the same order.
Gently stir everything to coat the bread with the egg mixture.
Crockpot: Cook on low for 3-4 hours or until a knife inserted in the center comes out clean. Uncover and cook for 10 minutes to help absorb the extra liquid.
Oven: Bake it in a preheated oven at 350° for 50-55 minutes. You can cover it with foil during the last 20 minutes to prevent it from getting too browned.
Serve warm with powdered sugar, vanilla ice cream, and caramel syrup. Or, when serving it for breakfast, use maple syrup and whipped cream.
Notes
If you do not have day-old bread, cut bread into cubes and bake them at 325˚F for about 5 minutes on an ungreased baking sheet.