Heat oven to 190C/170C fan/gas 5. Smear the butter all over the turkey crown and season all over with salt and half the five spice. Put in a roasting tin, skin-side up, and roast for 30 mins. While the crown is roasting, mix all the glaze ingredients in a bowl with the rest of the five spice.
Remove the crown from the oven and brush the skin generously with half the glaze. Continue to roast for another hour, glazing twice more, until cooked all the way through and the glaze is sticky and caramelised. Leave to rest for at least 20 mins before carving. Save the juices from the tin to make gravy.