1Remove the wing tips from the chicken using a knife and cut off the parson's nose.
2Turn the chicken onto its breast and cut along both sides of the backbone with kitchen scissors to remove it.
3Place the removed backbone and trimmings into a freezer bag for making stock later.
4Turn the chicken over, breast-side up, and flatten it by pressing down firmly on the breastbone.
5Pour water into a pot and add salt to create a 5% brine, heating it slightly until the salt dissolves, then adding ice and more water to cool it down.
6Add lemon, bay leaves, rosemary, and thyme to the cooled brine.
7Submerge the spatchcocked chicken in the brine and refrigerate overnight or for up to 24 hours.
8After brining, remove onions, garlic, herbs, and lemon from the brine and place them in a roasting tray.
9Drizzle olive oil over the aromatics in the roasting tray.
10Remove the chicken from the brine, pat it dry thoroughly with paper towels, and place it on top of the aromatics in the roasting tray.
11Drizzle olive oil over the chicken and rub it in.
12Place the chicken in the oven preheated to the highest temperature (around 200°C or 396°F) and cook for 30-35 minutes.
13Check the internal temperature of the chicken with a meat thermometer; it should be around 67°C (153°F) before resting.
14Remove the cooked chicken from the roasting tray and set aside to rest.
15For the gravy, remove the lemon pieces from the roasting tray with the drippings.
16Sprinkle plain flour (2-3 tablespoons) into the roasting tray with the drippings and cook out for about 5 minutes, stirring to create a roux.
17Deglaze the pan with white wine (around 100ml) and cook for another 5 minutes.
18Add chicken stock (around 500ml) to the pan and cook for another 5 minutes.
19Strain the gravy mixture into a saucepan and reduce it to your desired consistency.
20Carve the rested chicken by removing the legs.
21Remove the wings from the chicken.
22Cut along the side of the breastbone and then along the bottom to release each breast.
23Slice baked potatoes in half.
24Push the potato flesh through a fine-mesh sieve into a pot.
25Toss the leftover potato skins with balsamic vinegar, olive oil, and salt, then bake them into crispy snacks.
26Heat the sieved potato and gradually add cold butter (25-50% of the potato's weight) until incorporated.
27Slowly add warm milk (40% of the potato's weight) to the mashed potatoes until the desired silky smooth consistency is achieved.
28Serve a chicken leg with a portion of the mashed potatoes and generously drizzle with the prepared gravy.
Brine chicken for at least 8 hours, but no more than 24 hours to prevent it from becoming too salty.
Aim for an internal temperature of 60°C+ (140°F+) in the thickest part of the chicken before resting; it will rise above 70°C after resting.
Cook chicken at the highest oven temperature for about 30-35 minutes, keeping an eye on it.
For mashed potatoes, use a dry, fluffy potato variety like Maris Piper.
Push cooked potatoes through a very fine mesh sieve (like a '30 mesh' sieve) to achieve silky smooth mash without lumps.
When making mash, add 25-50% of the potato's weight in cold butter and then 40% of the potato's weight in warm milk until desired consistency is reached.