4- to 5-pound chicken
1 tablespoon salt
1/2 tablespoon pepper
1 tablespoon olive oil or canola oil
1 cup hard cider or apple juice
10 cloves garlic, left unpeeled
1/4 cup lightly packed sage leaves
1/2 whole cinnamon stick (about 3 inches long)
Zest from two medium lemons
2 1/4 cups whole milk
Remove the chicken from its packaging and pull the bundle of giblets from inside; discard or reserve the giblets for another use. Pat the chicken dry with a paper towel. Mix together the salt and pepper, and rub this all over the chicken.
→ At this point, you can sear the chicken for deeper flavor, or you can transfer it directly to a 6-quart or larger slow cooker, breast-side down. If you skip the searing step, reduce the amount of cider to 1/2 cup and don't use the olive oil.
To sear the chicken, warm the tablespoon of oil in a large skillet over medium to medium-high heat. Sear the chicken on all sides until deep golden-brown; use tongs to help turn it as you sear. The heat in the pan should be hot enough that you hear a constant sizzle as you sear the chicken; reduce the heat slightly if the oil begins to smoke.
Transfer the seared chicken to the bowl of a 6-quart or larger slow cooker and lay it breast-side down.
Pour off any grease left in the pan and return the pan to heat. Add the cider and scrape up any browned bits from the bottom of the pan as the cider simmers. Continue simmering the cider until it has reduced by roughly half. Pour the cider over the chicken.
Rub any loose papery skins from the garlic cloves, but otherwise leave them in their peels. Scatter the garlic cloves, sage leaves, cinnamon stick, and lemon zest on top of and around the chicken, then pour the milk over top.
Cover the slow cooker and cook for 4 to 6 hours on low heat.
To serve, lift the chicken from the slow cooker and transfer it to a cutting board; the legs or wings may fall off. Carve the chicken into pieces; you can leave the skin on or remove it, as you like.
Scoop the garlic cloves from the cooking liquid and scatter them over the chicken pieces. Transfer the liquid to a serving dish, straining if you'd prefer to remove the solid curds (although they're tasty!). Serve everything while still piping hot.