Remove the chicken from the fridge 30 minutes prior to cooking. Set the oven to 250°C/ 475°F.
Cut the potatoes into big wedges and line up in the roasting tray with the onions. Add 150 ml water to the pan with the potatoes and onions.
Place the chicken on top of the peeled vegetables. Rub with the 20g soft butter and place ½ a lemon and the bunch of thyme inside the chicken. If the chicken was brined don't season it, if it wasn't brined season liberally all over the skin.
Put the chicken in the hot oven and immediately turn down the heat to 200°C/ 400°F. Cook until the thigh meat reaches 165°F/ 74°C or the juices run clear in the leg meat when checked with a knife (Approx. 1 hour for brined and 1 hour + 15 for unbrined).
While the chicken is cooking you can make any additional side dishes or chill out for a bit.
When the chicken is ready, pull it out of the oven and carefully transfer the bird onto a plate with high sides. Cover the chicken with tin foil and let it rest for about 25 minutes in a warm place. Discard the onions from the potatoes and remove any liquid from the roasting dish. If there is liquid left over then save this for the gravy.
Add the oil to the potatoes and toss around in the pan. Check the seasoning on the potatoes. If you used a brined chicken the potatoes might be salty enough already. If not, season the potatoes and put back into the oven at 250°C/ 475°F for about 20-30 minutes or until golden brown.
Now start cooking the mushrooms in butter and brown them nicely. As soon as the mushrooms are browned, turn off the heat, hit them with the garlic, toss in the pan and deglaze with the red wine. Don't season this gravy until the end.
Reduce the red wine until most of the liquid has evaporated. Add the chicken stock and reduce by ⅓.
To finish the sauce, add the honey, the ⅛ tsp of xanthan and 1 tbsp of butter. Whisk until completely incorporated. Check the consistency. If it's too thin then cook it a little longer. Keep the sauce warm.
Once the potatoes have a beautiful golden colour remove from the pan and drain on paper towel.
Check the chicken again - all the those beautiful juices that dripped out the chicken while it rested need to go into the gravy. Add the juices and bring the gravy up to a boil before serving. Place everything to share on the table and carve the chicken at the table or slice it and serve it like in the picture. Enjoy!