To prepare leeks, arrange leek halves in an 8-inch baking dish; sprinkle evenly with 1/4 teaspoon salt and 1/4 teaspoon pepper.
Add broth and next 3 ingredients (through 1 thyme sprig).
Cut 1 (8-inch) square of parchment paper; lightly coat with cooking spray.
Place parchment over leek mixture, coated side down.
Bake at 325 for 50 minutes or until leeks are tender.
Let stand 5 minutes; drain cooking liquid through a sieve over a bowl, reserving solids.
Place cooking liquid in a small, heavy saucepan; bring to a boil. Cook until reduced to 1/4 cup (about 8 minutes). Chop cooked carrot; set aside. Coarsely chop cooked garlic; set aside.
To prepare dressing, heat oil in a small skillet over medium-high heat.
Add pancetta to pan; saut 5 minutes or until crisp. Stir in garlic and chopped leek; saut 2 minutes, stirring occasionally.
Sprinkle with sugar; saut 1 minute or until sugar dissolves. Stir in vinegar; simmer 2 minutes.
Add braising liquid, 1/8 teaspoon pepper, and dash of salt; simmer 2 minutes or until slightly thick.
Remove from heat. Arrange leek halves in a serving dish; sprinkle with carrot.