Whisk together the eggs, vanilla extract, milk, sugar and cinnamon in a shallow dish. Place the slices of bread in the mixture, turning to coat both sides so that they absorb the liquid.
Heat the butter in a nonstick frying pan. Use a palette knife or a fish slice to remove the soaked bread from the dish and fry the slices for 2 minutes on each side until golden. Cut the toasts in half diagonally into triangles, sprinkle with a little caster sugar and serve.