Place the parsley, garlic, thyme, rosemary, lemon zest, and two tablespoons of avocado oil into the mixing bowl. Chop for 10 seconds, Speed 5. Scrape down the sides of the bowl and repeat until finely chopped. Set aside.
Rinse the mixing bowl lightly.
Remove the skin from the breast in one piece. Set aside. Use a sharp knife to slice into the thick part of the breast, careful to not slice all the way through. Open the breast outwards to make a large flat surface. Cover with a sheet of clingfilm and pound out into a large rectangle about 1-inch thick.
Place several long sheets of clingfilm slightly overlapped on the workbench. Place the turkey skin, skin-side down into the centre of the plastic and stretch out evenly. Lift the turkey on top and spread the herb oil over the turkey. Season liberally with salt and pepper.
Roll the turkey tightly into a long cylinder. Stretch the skin evenly over the roll. Tuck the ends under. Place seam-side down and roll tightly enclosing in the plastic. Twist each end of the clingfilm and roll the turkey on the bench to shape into a tight cylinder. Place into the fridge and chill for a minimum of 3 hours or preferably overnight.
After chilling, remove the cling film and using kitchen twine, tie breast at 1.5-inch intervals. Tuck two of the sprigs of thyme under the twine in the centre.
Season generously with salt and pepper; and place the unwrapped turkey roll in the deep tray of the steaming attachment. Baste with some of the remaining oil, and put the lid in place.
Add 1000g of water to the bowl, and assemble the steaming attachment.
Steam for 45 min/120°C/speed 2.
Preheat the oven to 375°F / 180°C when there is 20 minutes left on the steaming time. Line baking tray with baking paper and set aside until needed.
After the turkey roll is steamed, discard the steaming water and carefully transfer it to the prepared baking tray. Bake for 20-30 minutes until browned and an internal temperature of 150°F / 65.5°C is reached. Transfer the turkey to a plate and leave to rest covered for 10 minutes before slicing.
Add the pan juices to the Thermomix bowl along with the broth and glucomannan powder. Cook for 4 minutes, 175° F / 80° C, Speed 2. If the gravy is not thickened to your liking by this stage, add more glucomannan, and cook for a further 2 minutes, 175° F / 80° C, Speed 2. Season to taste.