Preheat the grill (UK) / broiler (US) to as high a heat as it will go.
Crack your eggs into a bowl and beat with the mustard and worcestershire sauce.
Stir in the grated cheese and leave to one side.
Place the bread under the grill/broiler and toast on one side only for 5-10 minutes until it's done to your liking.
Flip the bread over and scoop the eggy-cheese mixture onto the soft, non-toasted side.
Place back under the grill/broiler and cook for 10-15 minutes until golden brown.