Pre-heat oven to 425 degrees.
In a small bowl, stir together all the spiced brown sugar rub ingredients.
Pat the chicken dry with a paper towel, place them on a cutting board and rub them all over with the spiced brown sugar mixture.
Heat butter in a large skillet over medium-high heat, until foaming. Add chicken, skin side down, and cook without moving it until well browned and crisp, about 8 minutes total, lowering heat if it starts to smoke excessively. Flip chicken and brown lightly on second side, about 3 minutes. Transfer chicken to a large plate and set aside.
Stir in balsamic vinegar and maple syrup until combined, then turn the heat off.
Nestle chicken back into pan, add the cranberries, pushing them aside so that as much chicken skin as possible is exposed. Add the rosemary sprigs. Transfer pan to oven and roast, uncovered, for about 25 minutes, until a thermometer reaches 165 when inserted.
Remove from the oven, taste sauce and season with salt and pepper.
Serve with the cranberries and sauce drizzled over the chicken thighs.