In a shallow bowl or pie plate, whisk together eggs, milk, vanilla, and salt.
Dip bread into egg mixture, coating each side.
Press both sides of bread into graham cracker crumbs.
Melt about 1/2 tablespoon of butter on a griddle or nonstick pan for each slice of bread. Cook until brown and crispy, then flip to other side, adding a little more butter to pan first.
While still hot, stack the slices of french toast, layering marshmallows and chocolate in between.