In a wide, shallow dish place the egg, ground cinnamon and vanilla extract. Whisk together well then pour in the milk and whisk in. Dip a slice of brioche into this batter, turning to coat, then place into the waffle iron. Repeat with another slice of brioche then close the waffle iron and leave to cook until golden brown (this took 4 minutes for me in the Cuisinart waffle maker). Remove the cooked French toast to a plate and repeat coating/cooking with the other 2 slices of bread.