Preheat the oven to 325
Bake or fry bacon until very crisp, reserve the fat, chop the crisped bacon finely and keep warm
In a saucepan over medium heat, bring 3 tbsp of fat to a sizzle
Add flour and cook until it just start to take color, ~1-2 minutes, whilst whisking to coat
Drizzle in the milk 1 tbsp at a time, whilst whisking.
Whisk in the worcestershire and mustard,
Thence working in batches, stir in and melt the cheeses
Stir in the chopped bacon
Taste, balance flavor and adjust texture with additional milk if necessary
Toast the bread until it has decent color.
Spread each slice of toast with a thick coast of the cheese sauce, and re toast until cheese is browned and bubbling.
Garnish with chives, or serve along with cranberry sauce / chutney