Preheat a grill on a high heat.

Melt the butter in a saucepan. Add the milk/beer and worcester sauce and stir for a few seconds. Add the cheese and tomato and gently cook on a medium heat stirring continuously until the cheese has melted (do not boil the mixture.) Remove from the heat and allow to cool for a couple of minutes before whisking in the egg yolks.

Lightly toast 4 slices of bread in a toaster or under a grill and spread the rarebit over the toast. Place under a hot grill for a bout a minute or 2 and serve.