Preheat oven to 200 degrees. Brush beef with oil and rub parprika over the entire roat. Season with salt and pepper. Roast beef for 20 minutes. Meanwhile, mix all ingredients except the sour cream in a bowl. Remove beef from oven, cover with mushroom mixture. Roast for a further 20 minutes on medium heat. Remove beef from pan leaving behind the mushroom mixture and cover to rest. Add the sour cream to the mushroom mixture and stir well to combine. Slice your beef and serve with lashings of mushroom gravy - divine!