Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper. Combine the first 6 ingredients in a bowl. Moisten your hands with cold water. Roll the meat into 1" balls and set on the baking sheet. Roast 20 minutes, or until cooked through.
Place the stock and flour in a pot and whisk to combine. Bring to a boil over medium-high heat. Reduce the heat until the mixture gently simmers. Whisk in the sour cream, salt and pepper. Add the meatballs, return to a simmer, and simmer 5 minutes. Spoon the meatballs into a serving bowl, sprinkle with parsley and serve.