In a medium mixing bowl, whisk together 4 large eggs, 1 cup of milk, 1 teaspoon of pure vanilla extract, and 1 teaspoon of ground cinnamon until combined and slightly frothy.

Slice the day-old sourdough bread into thick pieces, about 1-inch wide, and dip each slice into the custard mixture.

Melt 2 tablespoons of butter in a non-stick skillet over medium heat, watching for it to foam and turn golden brown.

Cook the soaked bread slices for about 3-4 minutes on each side until golden brown and crispy.

Remove the cooked French toast from the skillet and serve with fresh berries, whipped cream, and maple syrup.