Grease a 9x13" baking pan. Tear the loaf of bread into small chunks and scatter them into the pan. In a large bowl, whisk together the eggs, milk, half & half, sugars, vanilla and cinnamon until well combined. Pour the egg mixture evenly over the top of the bread chunks. Then cover it and place it in the fridge overnight.
In the morning, preheat the oven to 350F. Let the pan sit out at room temperature while the oven heats up. Bake it covered for 30 minutes, then remove the covering and bake for an additional 20-25 minutes, until the center is set and cooked through. If you'd like, you can dust some powered sugar over it before slicing it into squares and serving.
If you have leftovers, they will reheat really well. Just bake how much you want to reheat at 350F for 10 or so minutes.
