Preheat the oven to 300 degrees. Rub the BBQ spice mix on the front & back of the ribs. Place side by side on a large baking sheet. Wrap tightly in a double layer of aluminum foil, & bake for 3 hours. Let rest for about 10 minutes before unwrapping.
While the ribs are cooking, make the whiskey glaze. Melt the butter in a saucepan. Add the onion & season with salt and pepper. Sauté on medium heat for about 5-7 minutes, until the onions are lightly brown & caramelized. Add the minced garlic & cook for another minute. Mix in the garlic powder & chili powder - stirring it into the onions & butter. Mix in the rest of the glaze ingredients. Give it a good whisk. Bring the mixture to a boil, then reduce heat to low. Simmer for at least 1.5 hours, stirring occasionally.
Preheat your grill on high heat. Brush the ribs generously with the sauce & place on the grill. Grill for about 5 minutes on each side, basting each side liberally with the whiskey glaze. Alternatively, you can put them in the oven on broil for a few minutes on each side until they reach the char you'd like, basting liberally on both sides.