In a shallow bowl, whisk together the eggs, milk, vanilla extract, and ground cinnamon until well combined.
Place the crushed cornflakes in another shallow bowl.
Dip each slice of bread into the egg mixture, ensuring both sides are coated, then press each side into the crushed cornflakes to coat evenly.
Heat a large skillet or griddle over medium heat and add 1 tablespoon of butter. Once melted, add two slices of the coated bread to the skillet. Cook for 3-4 minutes on each side, or until golden brown and crispy. Repeat with the remaining butter and bread slices.
Serve warm with maple syrup and a dusting of powdered sugar if desired.