Preheat the oven to 160C/gas 3. Trim up the venison and cut into large chunks if not done already. Heat the oil in a large casserole and brown the meat all over. Remove the meat to a plate and add the onion and garlic to the casserole. Cook over a medium heat for about 15 minutes until the onion is just tinged with brown. Mix the paprika with the flour, thyme and juniper berries. Tip the meat and any juices back into the casserole, add the flour and paprika mixture, stir well and cook for a couple of minutes. Pour in the passata and beef stock, season well, stir and bring to the boil. Turn down the heat, cover with a lid and bake in the oven for about two hours. 20 minutes before it is ready, add the potatoes, replace the lid and cook for 20 minutes. Serve drizzled with soured cream and sprinkled with chopped parsley.