Melt-in-your-mouth, fall-off-the-bone BBQ ribs with the right balance of savory, sweet, & heat.
Combine all dry rub ingredients in a medium bowl and mix well.
Tear off three pieces of heavy duty foil at least 8 inches longer than the racks of ribs. Place them where you have easy access to them, shiny side facing down.
Using your hands, coat each rack of ribs thoroughly with the dry rub. Then place a rack of ribs in the foil, meat side facing down.
Transfer all ribs to an aluminum roasting pan. If you have three racks of ribs, you can stack the third one right on top of the other two.
Refrigerate overnight or at least 12 hours.
Place baking tray with ribs in the oven. Cook at 350 for the first 30 minutes, then reduce heat to 300 and bake for another 90 minutes.
At this point check to be sure the ribs are done: leaving the ribs in the baking tray, carefully open one end of one foil packet. (Be careful the steam is extremely hot.) You should see that the meat has started to pull away from the bone. Gently test with a fork to ensure that they are tender and give easily, but still hold their shape to be able to survive grilling or broiling. If they need more time, re-seal the foil and return them to the oven for another 15-30 minutes.
Carefully pour all the cooking liquid from the ribs into a Pyrex measuring cup and set aside.
In a saucepan add the mustard, vinegar, ketchup, brown sugar, garlic, black pepper, and 1 cup of drippings from the ribs. Bring the sauce to a gentle boil then reduce and allow to simmer for around 10 minutes.
Gently turn the ribs over, meat side down. Brush the bone side of the ribs with a small amount of BBQ sauce. Leave the grill open, and closely monitor the ribs during this step! Grill the ribs long enough to caramelize, without burning them. You may need to adjust grill heat as necessary to achieve this, but normally this takes around 5 minutes. Place the grilled ribs bone-side down onto a cookie sheet, then re-apply BBQ sauce over the meat side.