Start by preheating your oven to 350°F (175°C) and lightly greasing a 9x13 inch baking dish.
In a spacious mixing bowl, blend together ground beef, ground pork, finely chopped onion, breadcrumbs, an egg, and milk. Season the mixture with parsley, Worcestershire sauce, two teaspoons of salt, and one teaspoon of pepper. Use your hands to combine everything thoroughly.
Shape the mixture into small balls, about the size of walnuts, and arrange them in the prepared baking dish.
Bake the meatballs in the oven for 30 minutes, turning them occasionally to ensure they brown evenly on all sides.
While the meatballs are baking, prepare the sauce by heating oil in a saucepan. Add flour, paprika, one tablespoon of salt, and one teaspoon of pepper, cooking over medium heat until it starts to sizzle.
Gradually mix in hot water and sour cream, stirring until the sauce is smooth and heated through.
After the meatballs have been baking for 30 minutes, pour the creamy sauce over them and return the dish to the oven for an additional 20 minutes, stirring occasionally to keep the meatballs coated.