Set aside a shallow dish with caster sugar, egg, and vanilla essence.
Press the other slice of bread firmly against the jam-covered slice of bread.
Over a medium heat, melt the butter.
For the sandwich to absorb all of the egg mixture, it needs to be soaked in it for some time.
Cook each side for 1-2 minutes in butter.
Sprinkle the extra caster sugar over the sandwich after slicing it in half.
Served alone, with ice cream, yogurt, or whipped cream, or with a scoop of ice cream.