Peel the thin membrane from the back of the ribs (very important, don't skip this step!)
Cut each rack of ribs in 1/2. Rub all 4 pieces with Herbie's American Spicy BBQ Rub.
If using an Instant Pot:
Place the ribs in the bowl of an Instant Pot.
Pour in the root beer. Set Instant pot to Meat/Stew setting.
Release the pressure, remove the ribs and place on a parchment lined sheet tray.
Preheat oven to 350 degrees.
Place ribs in a an oven proof glass casserole dish. Pour in root beer and seal tightly with aluminum foil.
Cook for 3 hours until ribs are easily pierced with a fork, but not falling apart. Place ribs on a parchment lined sheet tray.
While ribs are cooking, place the blackberry preserves, soy sauce and balsamic vinegar in a small sauce pan over medium heat and whisk to combine. Let glaze simmer and reduce by 1/3. Turn off the heat and whisk in the butter.
Brush the glaze on the ribs and bake at 400 degrees for 10 minutes, brushing with the glaze again halfway through. Remove from the oven, brush with a little more glaze and serve with your favorite slaw or potato salad.