These meatballs taste like beef tenderloin with horseradish sauce but are easier to eat—and a lot less expensive.
Preheat the oven to 425°. Line a baking sheet with parchment paper.
In a medium bowl, mix the breadcrumbs and half-and-half. Let stand until the crumbs soften, 3 to 5 minutes. Add the beef. Season with salt and pepper. Mix in the parsley, onion with juices, Worcestershire, egg yolk, and garlic. Roll the mixture into balls about the size of a large walnut. Arrange on the baking sheet; spray with cooking spray or brush with oil. Roast the meatballs, turning once, until browned and just cooked through, about 18 minutes.
While the meatballs are roasting, in a medium bowl, mix the sour cream, chives, and beet horseradish. Season the sauce.
Serve the meatballs with the sauce for dipping or topping.