In a large bowl, whisk together eggs, milk, sugar, vanilla, salt, and cinnamon until smooth. Set aside.
Add cornflakes to a large zipper bag. Remove the air from the bag and seal it shut. Use a rolling pin (or your hands) to slightly crush the cornflakes into a smaller crumb. You should get about 2½ cups of crushed cornflakes.
Add the crushed cornflakes to a plate in an even layer.
Heat griddle over medium heat, about 350°F. Add 2 tablespoons of butter to the griddle.
Working in batches, dip slices of bread into the egg mixture (not soaking the bread) and then into the cornflakes. Press down slightly so the crumb sticks.
Place the bread on the hot griddle and cook for 1 to 1½ minutes on each side or until golden brown. Add more butter before cooking the next batch.
Serve with room temperature butter, syrup, or fresh fruit. Best served hot.