In the measuring up of the buttermilk, whisk it with the garlic, salt, sugar, paprika and lots of freshly ground black pepper. Place all the chicken parts in a gallon-sized freezer bag (or lidded container) and pour the buttermilk brine over them. Swish it around so that all parts are covered. Refrigerate for at least 2 but preferably 24 and up to 48 hours (as mentioned earlier, we tried an extra 24 hours without incident).
When ready to roast, preheat oven to 425°F (fan on for convection). Heat up a cast iron skillet on medium high heat. Add in the goose/duck fat if using, drizzle over some olive oil. Remove chicken from buttermilk brine, shake off excess and arrange skin side up on the skillet. Turn off heat. (If using a baking dish, just arrange the chicken in it skin side up.) Drizzle lightly with olive oil, then sprinkle with additional paprika and sea salt to taste.
Roast for 20 minutes if using cast iron skillet or 25-30 minutes if using baking dish, until brown and done. Garnish with herbs of choice if using, serve immediately with pan drippings over some potatoes or greens.