Preheat the broiler. Place the bread slices on a baking sheet and toast them in the oven for 5-10 minutes, or until golden.
Meanwhile, stir together the butter, cheeses and Worcestershire. Take the toasted bread out of the oven, flip them over, and spread the butter-cheese mixture thickly over the untoasted side. Return to the oven for another 5-10 minutes, until the cheese is bubbly and the toast is golden around the edges.
Cut into whatever sized pieces you like and serve immediately. Serves 4.