Mix processed cheese food, Cheddar cheese, bacon, Worcestershire sauce, and dry mustard together in a bowl.

Heat skillet over medium heat.

Butter both sides of each slice of bread and toast in skillet until browned, 1 to 2 minutes per side; arrange onto a baking sheet. Repeat toasting with remaining butter and bread slices.

Set oven rack about 6 inches from the heat source and preheat the oven's broiler.

Spoon cheese-and-bacon mixture atop the toasts. Arrange toasts on a baking sheet.

Heat toasts under the broiler until the topping is hot and bubbling, about 2 minutes.