Place 4 slices of provolone cheese over the (4) bottom slices of the challah bread, followed by the ham. Top with the (4) top slices of bread.
In a pie plate or shallow dish, whisk together the milk, eggs and cinnamon until well combined.
Grease a nonstick skillet, cast-iron skillet, or griddle with cooking spray or oil and heat over medium heat. Dip each sandwich into the milk mixture, allowing the bread to soak up the liquid, then turn over and repeat on the other side and shake off the excess mixture. Place in the skillet and cook for 2-3 minutes per side or until golden brown and the cheese has melted.
Place each on a plate and dust with the powdered sugar, if using. Serve with apple butter.