Add the eggs, milk, granulated sugar, salt, cinnamon, and vanilla extract to a separate shallow dish.
Whisk until the egg mixture is well-combined.
Dip both sides of a piece of bread into the egg mixture.
Gently press the bread into the crushed cereal, flipping to coat each side.
Repeat with remaining bread, egg mixture, and crushed cereal. Work in batches if necessary.
Melt enough butter to coat the skillet.
Place pieces of the cereal-coated bread in the skillet and cook until one side is golden brown.
Flip and continue to cook until the second side is also golden brown.
Serve with desired toppings.
Notes
Cornflakes: Finely crushing the cornflakes will give you a more even coating.
Sugar: The sugar helps the cornflake coating to caramelize as it cooks.
Bread: It's important to use thick-sliced bread as it holds up better than sandwich bread. Sandwich bread can be too soft and can tear from the egg mixture.
Milk: Any type of milk, including nondairy milks like almond milk, will work in this recipe.