Like cheese on toast but richer (and better).

Prep

1. Tip the butter into a bowl. Soften and cream it with a wooden spoon. Add the egg yolk and mustard. Cream them together. Add Guinness or milk. Cream that in.
2. Add the finely grated cheese. Cream and stir until you get a thick paste.
3. Slice the bread. Pre-heat the grill.

Cook

1. Grill the bread slices until browned on one side. Remove.
2. Spread mix smoothly over the untoasted side of the bread taking it right up to the edges to prevent burning. If making 2 slices, save one third of the mix for another day.
3. Put the grill pan in lowest position and cook until the rarebit is golden brown bubbling and cooked through. Adjust the heat up or down as you need to. It should take 1-2 minutes.

Plate

1. Eat while piping hot. This is good with a crisp pear on the side.