Preheat the oven to 250˚F.
Place each rack of ribs on a large square of aluminum foil and sprinkle generously with salt. Top with a few sprigs of thyme, then wrap up tightly. Place the wrapped racks on baking sheets, and bake for 3-4 hours, until very tender. Remove from oven and set aside to cool before opening the packets.
While the ribs are baking, combine the balsamic vinegar, honey, ketchup, and beer in a large saucepan. Stir in the garlic, red onion, brown sugar, molasses, mustard, hot sauce, Worcestershire sauce, and water. Bring to a simmer over medium-low heat, stirring occasionally. Simmer gently for 2-3 hours, until the sauce is thick.
Turn on the broiler (see note). Slice the racks into individual ribs and place them on a foil-lined baking sheet. Brush very generously with the sauce. Set under the broiler and broil for just 3-4 minutes, keeping a close eye on them, removing them just before they turn black - with all the sugar they can burn quickly.
Serve hot, with lots of napkins!