Preheat oven to 350℉. Lightly grease a large casserole dish.
Combine all the ingredients for the meatloaf in a large mixing bowl. Form into a fairly tight loaf and place in the center of the casserole dish. Cover and bake the meatloaf in the oven while preparing the sauce.
In a large bowl, combine all the sauce ingredients. Whisk to combine. Carefully pour the sauce over the top of the meatloaf in the oven. Bake uncovered for 1½ hours.
Allow the meatloaf to rest 15 minutes before serving. Garnish with parsley and serve with mashed potatoes.