"Rachael Ray's Beef Meatballs with Pink Horseradish Sauce"

Ingredients

• About 3/4 cup stale white breadcrumbs or panko breadcrumbs
• ⅓ cup half-and-half or whole milk
• 1 lb. ground sirloin (90% lean)
• Kosher salt and coarsely ground black pepper
• ¼ cup (a small handful) fresh flat-leaf parsley leaves, finely chopped
• About 3 tbsp. grated onion with juices
• 2 tbsp. Worcestershire sauce
• 1 large egg yolk
• 1 large clove garlic, grated or finely chopped
• Cooking spray for spraying, or vegetable oil for brushing
• 1 cup sour cream or Greek yogurt
• ¼ cup finely chopped fresh chives
• 3 tbsp. beet horseradish (such as Gold's)