I got the idea for crumpets with a savoury topping from a magazine recipe. The harissa reflects my perverse taste for chilli with everything, and is obviously optional - though a pinch or two of cayenne pepper would be a nice, less controversial alternative.
The egg causes the mixture to puff up appealingly. If you were using twice as much cheese, you might mix it with a whole beaten egg rather than with two yolks.
Makes three crumpets
80g grated cheese, such as Cheddar or Gruyere
1 egg yolk
(Also possible, instead of the harissa: Worcester sauce, nutmeg, black pepper, cayenne)
Toast the crumpets. Mash up the cheese and other ingredients with a fork.
Spread the mixture on the crumpets, and grill (I use the lowest setting) until puffed up and browned.