In the same pan, melt the butter over a medium heat until foaming. Add the nutmeg, mustard powder, paprika, thyme and flour, and season. Cook for 1 min, until fragrant. Slowly add the milk, bit by bit, whisking constantly, until you have a smooth, thick sauce. Remove from the heat, and stir in the cranberry sauce, cheddar and pancetta, mixing well. Season with a little salt and lots of black pepper. Scrape into a shallow bowl, then cover and chill in the fridge for about 2 hrs or ideally overnight, until cold and solid.
