To make the glaze, put the Guinness, honey and sugar into a pan. Reduce by almost half to form a sweet syrupy glaze, then allow to cool.
Heat oven to 200C/fan 180C/gas 6. Season the pork with pepper and salt, if you want, place on a baking tray and roast for 20 mins. Then turn the heat down to 160C/fan 140C/gas3. Remove the pork from the oven and brush all over with most of the glaze (reserving a few tbsp) cook for a further 40-50 mins, brushing and basting the pork as it cooks until it’s beautifully caramelised and glazed.
Remove the pork from the roasting tray and leave to rest. Pour the remaining glaze into the roasting tray, then add the wine, Champagne or water. Place the pan on the heat and bring everything to the boil, simmer for a few mins until you have thick gravy. Carve pork into thin slices and place on top of the colcannon (see separate recipe). Glaze with the Guinness syrup, drizzle a little on the plates and finish with a sprig of parsley.