Gather a group of shallots, leeks, scallions and an onion—as many members of the allium family as you have on hand—and chop them into a small heap. Add a minced clove of garlic. Grate a few generous handfuls of the best cheddar you can afford, set a little aside, and gently combine the rest with the onion mixture.
Butter one side of each piece of thickly sliced bread and heap as much of the mixture as possible between the slices (butter facing in). Spread a thin layer of mayonnaise on the outside of the bread (this will keep it from scorching on the griddle). Press the reserved grated cheese to the outside of the bread, where it will create a wonderfully crisp and shaggy crust, giving your sandwich an entirely new dimension.
Fry on a heated griddle or in a skillet about 4 minutes a side, until the cheese is softly melted.
Makes 1 sandwich
Taken from My Kitchen Year, Random House 2015