For the turkey breast: Preheat the oven to 400 degrees F.
Break down the turkey by removing the breasts while keeping the skin on. Remove the turkey legs and thighs and set aside.
Sprinkle the turkey breasts on both sides with the salt and pepper. Heat a large cast-iron pan over medium-high heat, and add the butter. Melt the butter and cook, stirring frequently to it butter does not burn, until it starts to brown, about 5 minutes. Once the butter stops bubbling, add the turkey breasts skin-side down and turn the pan down to medium. Sear for about 5 minutes, then flip the breasts over and cook until golden brown. Add the whole garlic cloves and sage to the pan and baste a few times. Transfer the pan to the oven for 8 minutes.
Flip the breasts back over to skin-side down and cook, basting, on the stovetop, about 4 minutes.
Finish in the oven skin-side down until an instant-read thermometer inserted in the thickest part registers 160 degrees F, another 5 to 7 minutes. Flip and baste, then remove from the pan.
Let rest 4 to 5 minutes. (Leave the oven on.)
For the turkey legs: Sprinkle the legs and thighs with the salt and pepper. Heat a large skillet over medium-high heat. Add oil to coat the bottom of the skillet. Add the legs and thighs and sear until golden brown, about 3 minutes on each side, then remove the legs and thighs and place in a pressure cooker. Remove half of the oil from the skillet and turn the heat down to medium. Add the garlic and onions to the skillet and saute until fragrant, about 1 minute. Add the garlic and onions to the pressure cooker. Add the wine to the skillet and deglaze, using a spatula or wooden spoon to get all the brown bits off the bottom of the skillet. Then, add the pan sauce to the pressure cooker along with the stock, sage and bay leaves. Seal the pressure cooker and cook according to the pressure cooker instructions on medium for 25 minutes.
Remove the legs and thighs to a bowl. Remove the meat from the bones and shred. Set aside.
Strain out the juice and set aside to make gravy.
For the hash: Mix together the oil, salt, pepper, garlic, parsnips, carrots, onions and celery root in a bowl. Spread out on a sheet tray and bake until tender and starting to brown, 10 to 14 minutes. Meanwhile, brown the butter in a small pot over low heat. Toss the veggies and shredded turkey leg meat in the brown butter along with cider vinegar and sage.
For the gravy: Bring your strained stock to a simmer in a medium saucepot. Melt the butter in a small pot and whisk in the flour and vinegar. Cook until deep brown, 5 to 10 minutes. Whisk the roux into the stock and bring to a rolling boil, then boil for about 5 minutes. Season to taste.
Place the hash on the plate. Slice the turkey breast on a bias and lay over the top of the hash. Drizzle the gravy over that. Top with the chives.