8 large garlic cloves
2 T. finely chopped rosemary
2 T. packed brown dark brown sugar
2 T. balsamic vinegar
1 tsp. cayenne
8 lb. baby back pork ribs (8 racks)
1 c. water
Mince and mash garlic to a paste with 1 tsp. salt. Stir together with rosemary, brown sugar, vinegar, cayenne, 1 T. salt and 1 tsp. pepper. Rub evenly all over ribs and transfer to roasting pans. Marinate, chilled 8-24 hrs. Preheat oven to 425 degrees with racks in upper and lower thirds. Pour 1/2 c. water into each roasting pan and tightly cover pans with foil. Roast ribs, switching position of pans halfway through, until meat is very tender, about 1-3/4 hrs. Remove pans from oven and transfer ribs to a platter.
To make glaze:
add 1 c. hot water to each roasting pan and scrape up brown bits. Skim off and discard fat, then transfer liquid to a 10-inch skillet. Add 1 c. balsamic vinegar and 1/2 c. brown sugar and bring to a boil, stirring occasionally. Boil and reduce to about 1 c., about 15 min. Serve.