Whisk the custard: In a bowl, whisk together half-and-half, egg, vanilla, salt, and cinnamon until smooth.
Soak the bread: Pour the mixture into a shallow dish. Add 2 bread slices, pressing down gently. Soak for 2 minutes per side.
Cook the toast: Heat a skillet over medium heat. Melt 1½ tbsp butter, then add the soaked bread. Cook for 4 minutes per side until golden.
Repeat: Repeat with remaining slices, adding more butter as needed.
Serve warm with maple syrup, fresh berries, or your favorite toppings.