For Meatballs
1 pound 85% lean ground beef
1 pound ground pork
½ cup Kikkoman® Panko Bread Crumbs
½ cup grated yellow onion
1 large egg
1 teaspoon salt
½ teaspoon black pepper
½ teaspoon garlic powder
½ teaspoon allspice
½ teaspoon nutmeg
For Cooking
2 tablespoons olive oil
For Sauce
3 tablespoons unsalted butter
3 tablespoons all-purpose flour
3 cups reduced sodium beef stock
2 tablespoons Kikkoman® Soy Sauce
1 teaspoon Worcestershire sauce
1 tablespoon Dijon mustard
¼ teaspoon black pepper
½ cup sour cream
2 tablespoons fresh chopped parsley, for serving