Make the barbecue sauce by combining all ingredients except ribs in a medium saucepan over medium heat. When it comes to a boil, reduce heat and simmer, stirring often, for 45 to 60 minutes or until sauce is thick.
Preheat your oven to 135°C.
Brush sauce over the entire surface of each rack of ribs. Wrap each rack tightly in aluminum foil and arrange the packets on a baking sheet, with the seam of the foil facing up.
Bake for 2 – 2½ hours or until the meat on the ribs has pulled back from the cut ends of the bones.
When the ribs are almost done, preheat your grill to medium heat.
Remove the ribs from the foil (careful – the liquid inside will be hot!) and grill them for 4 to 8 minutes per side, or until the surface of the ribs begins to char.
Brush sauce on both sides of the ribs for a few minutes before you remove them from the grill. Be sure not to brush on the sauce too soon or it could burn.