In a 10-inch cast iron skillet, cook the bacon over medium heat until crisp, about 5 to 6 minutes. Remove the bacon with a slotted spoon, and set aside. Reserve bacon fat in pan.
Cook pasta per manufacturer directions.
Whisk flour into the rendered fat. Cook whisking constantly, 2 minutes. Whisk in the milk, salt, mustard, hot sauce and Worcestershire. Bring to a simmer whisking constantly until thickened, almost 15 minutes.
Remove from heat. Add both cheeses and stir until melted and smooth. Stir in bacon, chives and cooked macaroni.