The Welsh Rarebit Recipe
Place a saucepan over low heat. Add 1 tablespoon of the butter and, once it has melted, add the leek. Cook for 5 minutes until softened. Remove 2 tablespoons of the leeks and let sit for later. Add the flour, mustard powder and paprika to the remaining leeks and cook for 1 minute. Next, add the stout to the pan, stirring all the time as the mixture starts to thicken. Add 3/4 of the cheese, along with a good dash of Worcestershire sauce or Tabasco. Continue to cook slowly until the cheese has melted. Pour the mixture onto a rimmed baking sheet. Let it cool slightly, then transfer to the fridge to set for about 20 minutes. When it's ready, it should be thick enough to spoon. Meanwhile, butter the bread. Preheat the broiler to high. Divide the cheese mixture between all 4 slices of bread, then pop under the broiler for 3 to 5 minutes, until bubbly and golden. Top with the leeks and scallion and serve.
For a "closed" sandwich version, just press the slices together, butter the outsides of the bread and finish in the skillet instead of under the broiler.
From Melt It, by Becks Wilkinson, published by Kyle Books.