Chicken with 40 Cloves is an old French classic. Plenty similar versions exist online and in every French cookbook. Here is Nigella’s from Food Network. Be sure to use bone-in chicken with the skin. Boneless/skinless will result in a much blander dish.
Preheat the oven to 350 degrees F.
Heat the oil on the stovetop in a wide, shallow ovenproof and flameproof Dutch oven (that will ultimately fit all the chicken in one layer, and that has a lid), and sear the chicken over a high heat, skin-side down. This may take 2 batches, so transfer the browned pieces to a bowl as you go.
Once the chicken pieces are seared, transfer them all to the bowl. Finely slice the scallions, put them into the Dutch oven and quickly stir-fry them with the leaves torn from a few sprigs of thyme.
Put 20 of the unpeeled cloves of garlic (papery excess removed) into the pan, top with the chicken pieces skin-side up, then cover with the remaining 20 cloves of garlic. Add the vermouth (or white wine) to any oily, chickeny juices left in the bowl. Swish it around and pour this into the pan too. Sprinkle with the salt, grind over the pepper, and add a few more sprigs of thyme. Put on the lid and cook in the oven for 1 1/2 hours.
Make Ahead Note: Chicken can be browned and casserole assembled 1 day ahead. Cover tightly and store in the refrigerator. Season with salt and pepper and warm the pan gently on the stovetop for 5 minutes before baking as directed in recipe.
Making Leftovers Right: If I do have any chicken left over – and I don’t think I’ve ever had more than 1 thigh portion – I take out the bone then and there and put the chicken in the refrigerator. Later (within a day or two), I make a garlicky soup, by removing the chicken, adding some chicken broth or water to the cold, jelled juices, placing it over a high heat and, when that’s hot, shredding the chicken into it and heating it through thoroughly, till everything is piping hot. You can obviously add rice or pasta. Otherwise, mash any leftover garlic into the concentrated liquid (which will be solid when cold), chop up some leftover chicken, and put it all into a saucepan with some cream. Reheat gently until everything is piping hot, and use as a pasta sauce or serve with rice.