Heat a large saucepan over medium-high heat. Add 2 tablespoons canola oil to pan, and swirl to coat. Add onion and garlic; sauté 5 minutes, stirring constantly. Add sugar and the next 10 ingredients (through star anise); bring to a boil. Reduce heat, and simmer, partially covered, for 30 minutes or until plums break down and sauce thickens, stirring occasionally. Discard cloves and anise.
Preheat oven to 450°.
Heat a large skillet over medium-high heat. Add 2 tablespoons oil to pan; swirl to coat. Sprinkle pork evenly with 1/2 teaspoon salt and 1/2 teaspoon black pepper. Add pork to pan; sauté 7 minutes, turning to brown on all sides.
Transfer pork to a foil-lined jelly-roll pan; coat with 1/2 cup plum sauce. Roast pork at 450° for 15 minutes. Remove pork from oven. Turn pork over; coat with an additional 1/2 cup plum sauce. Roast 10 minutes or until a thermometer inserted in thickest portion of pork registers 155°. Remove from pan; let stand 10 minutes.
Serve with remaining plum sauce.