The ingredients for these three sandwiches were:
80g Gruyere, grated
2 egg yolks, beaten
Few splashes Worcester sauce
Cayenne and/or black pepper, if you like
Packeted, sliced bread works particularly well, I am afraid. Cut off the crusts. Mash the ingredients, and spread them on half of the slices, in the centre. Lay the other slices on top. You may find with this kind of bread that you can squidge the edges together.
Melt a knob of butter and a little olive oil in a frying pan, over a low to medium heat. (Use no more fat than you want to eat, because the bread will absorb it all.) Slip in the sandwiches, and fry until brown beneath - 2 to 3 minutes.
Remove the sandwiches, and add a little more butter and oil. The butter may sizzle rapidly, so to keep it from burning you may need to remove the pan from the heat. Fry the other sides of the sandwiches.