Heat the oven to 180C (fan)
Butter one side of the bread and lay it butter side down on a baking tray.
Mix the grated cheese, beaten egg, mustard and black pepper together.
Place some ham on top of the bread *my ham was thick so I tore it into small pieces, but if it's thin you can do a whole slice
Divide the mixture evenly between the slices of bread, spreading it right up to the edges.
Bake for around 15-18 minutes, until the cheesy topping is golden brown and puffed up and the bread is crisp
