Combine first 5 ingredients in a small bowl, stirring until blended. Stir in 1/2 cup walnuts.
Toss together garlic and next 6 ingredients; drizzle with olive oil. Sprinkle with sea salt and pepper. Spoon mixture into a 3-quart baking pan. Bake at 400° for 25 minutes, stirring once. Dollop goat cheese mixture over onion mixture; bake 20 minutes or until onions are tender.
Remove from oven; sprinkle with remaining walnuts. Garnish, if desired.
* Cipollini are bittersweet bulbs of the grape hyacinth. They look and taste like small onions. Shallots may be substituted.