To make the glaze: Combine piloncillo, water, chipotle puree, and garlic in a small saucepan. Bring to a simmer. Cook uncovered, over low heat until the syrup has thickened, about 20 minutes. Let cool.
To make the ribs: Preheat oven to 300°F. Mix barbecue sauce with 4 tablespoons glaze. Set aside.
Place ribs on baking sheets, meaty side up. Combine ancho chile powder, salt, and black pepper. Rub minced garlic over ribs, then sprinkle with spice mixture. Drizzle with olive oil and ensure ribs are coated well with garlic and spices.
Bake uncovered in oven for 2 hours. At this time, begin to brush glaze mixture onto the ribs every 15 minutes for 30-45 minutes.
Once glaze has thickened, slice ribs, serve.