Sometimes, you just can't beat those good old, classic combinations. Take ham and cheese: it's one of those marriages made in culinary heaven, and although the pair can be teamed in a number of ways, the croque monsieur must surely be the king of them all. This one is a true Parisian version: salty slices of ham with a sumptuous, oozing Gruyère bechamel, with a little mustard in the mix to add a lovely, sharp tang. All this loveliness is sandwiched between slices of buttery bread, fried to retain to retain the all-important crunch. Sure, you could toast them, but for proper indulgence, you shouldn't wimp out. You should use butter, too, which imbues the bread with a slightly nutty taste. Eat your croque hot and bubbling, to best appreciate its rich, molten centre.