In a shallow dish with sides, like a pie dish (or similar), combine the milk, cornstarch, vanilla, and cinnamon. Whisk until everything is combined and the cornstarch dissolves.
Place the bread slices in the milk mixture and soak each side for about 15 seconds. In the next step, when you lift the bread slices from the dish onto the pan, let any excess liquid drip back into the dish to keep the French toast from getting soggy.
Cook:
Melt 1 tablespoon of butter in a non-stick pan. Place the soaked bread slices in the pan and cook over medium heat for 3 to 4 minutes on the first side, until the bottom lifts easily and turns golden brown.
Using a spatula, flip the French toast pieces over and cook the second side for another 3 minutes. You'll know they're cooked through and ready to be removed from the pan when the middle feels puffy. Remove them from the pan and transfer to a plate.
Serve:
Top the French toasts with berries, syrup, or your favorite toppings.