Slice challah into ¾" slices. Then prepare the wet mixture by adding eggs, milk, vanilla, salt, and cinnamon-sugar mix into a glass pie pan or square baking dish (any shape is fine as long as it is more shallow then deep).
Heat large frying pan over medium heat and then melt about ½ TB of butter in the pan.
While the butter is melting, dip a piece of bread into the milk mixture, pressing down to make sure both sides of bread are soaked and then transfer to the hot pan. Repeat with additional pieces of bread until pan is full.
Cook until each piece is golden brown, then flip and cook until golden brown on second side. Repeat the steps (melting butter, soaking bread, and frying) until you have used up all the bread.
Move to serving dish and enjoy!
Notes
Make Ahead: You can make this dish up to an hour before you are going to serve it. Reheat the cooked french toast on a baking sheet covered with foil in a low oven just until warm. You don't want to dry out the french toast so watch it carefully.Cooking Tip: Try not to crowd the pan while cooking the french toast. It will take longer for the pieces to cook and they will likely cook and brown unevenly. I suggest 3-4 pieces of bread at a time.Make it dairy free: You can easily substitute plant based butter and plant based milk