Lay chicken backs and feet onto sheet tray and roast at 475F/245C for 30-40min.

Place chopped onion, carrots, celery, and leek onto tray. Toss with olive oil and roast at 475F/245C for 30 minutes until caramelized.

Add roasted vegetables and chicken bones/feet and veg into slow cooker along with chicken and veg fond from roasting trays. To work up fond, pour off excessive fat (from chicken tray) then add about 1qt/L water onto tray and scrape up fond with a wooden spoon. Add to slow cooker. Add tomato paste and water to cover. I use about 5qt/L in my 8qt cooker.

Slow cook for 12 hours.

Strain out liquid and skim off fat from top. Refrigerate until ready to reduce.

When ready to reduce stock, add it to large heavy-bottomed pot. Add 3 packets (20-28g) of gelatin mixed in water at this point if you didn't use chicken feet in your stock. Bring to boil and simmer over medium heat for 45min to1 hour to reduce, stirring every 15 minutes.

When ready, stock should have reduced significantly, bubbles should be large and glossy, and a spoon pushed through should leave a trail. Transfer glace to a small sauce pan over medium heat and add butter. Swirl as butter melts to emulsify. Stir in a pinch of salt.

Add water, salt, sugar, garlic, and herbs to a sauce pan and bring to a boil. Continue to simmer for 10 minutes, then turn off heat and allow to seep for another 5min.

Add ice into a large (at least 4qt/3.5L) container. After brine has seeped, pour it over the ice. When melted the brine is ready.

Add deboned chicken halves to brine, refrigerate, and allow to brine for 4 hours.

After 4 hours, remove chicken from brine and dry as much as possible with towels (and blow dryer on cool setting for extra credit - you want the outside of the bird to be VERY dry). Refrigerate uncovered to dry further until ready to cook.

Preheat oven to 475F/245C - turn on vent hood if you have one.

Add 3Tbsp canola or vegetable oil to preheated heavy (12") stainless or cast iron pan over high heat.

Carefully lay in 1 half of chicken skin side down and press to ensure contact. After 2-3mins, after skin has taken on golden color, transfer pan to preheated oven to roast for 7-8min.

To finish, return pan to stovetop over medium heat and flip chicken to skin side up. Add butter and several more sprigs of rosemary, thyme, and sage. Baste skin side with herb butter for 3-4 min as shown @12:13.

When done, internal breast temp should be 150F/65C. Place chicken on wire rack, pour over herb butter left in pan, and allow to rest for 5min. Top with generous amount of chicken jus (glace).