Take the turkey breast out of the fridge and allow it to come to room temperature for an hour before you start.
Heat the oven to 190C/170C fan/gas 5.
Weigh the turkey breast and calculate 40 mins per kilo plus an additional 20 mins.
Put the onions, shallots, parsnips, carrots and rosemary leaves in a roasting tray and rest the turkey breast on top.
Rub the room temperature butter over the skin and season well. Use a bit more salt than you think you need because it gives the skin a lovely finish.
Lay the streaky bacon on top of the buttered roast.
Roast in the oven for the allotted time.
Life Hack – Leave the turkey to rest for 20 mins somewhere warm after you remove it from the oven. This is crucially important for flavour, succulence and ease of carving. If you carve it too early the juices will simply run out of the meat and you'll be left with a dry bird.