In small nonstick skillet combine 1/4 cup onion and 1/4 teaspoon garlic and cook, stirring constantly, until onion is soft but not brown.
Transfer to medium bowl and add pork, bread cubes, sour cream, parsley, salt, rosemary, and pepper; stir to combine.
Form mixture into 8 pork balls, about 2 1/2-inch diameter each; arrange pork balls on rack in broiling pan and broil 6 inches from heat source, turning once, until browned.
In 10-inch skillet heat oil; add remaining 1/4 cup onion and remaining garlic and saute until onion is soft.
Add pork balls and toss with onion; stir in crushed tomatoes and Worcestershire sauce.
Cover and let simmer for 30 minutes, turning pork balls once