Hamburger Soup

In a large pot over medium-high heat, heat oil. Add ground beef and cook, breaking up with a spoon, until golden, about 8 minutes. Season with salt and pepper. Using a slotted spoon, remove the beef to a plate. Add the onion, potatoes, carrots, celery, and garlic and season with salt and pepper. Cook, stirring occasionally, until vegetables are soft, about 5 minutes. Add the tomato paste and cook, stirring, 1 minute. Return the beef to the pot. Pour in broth and diced tomatoes, with juices, stir to combine. Add the Italian seasoning and bring to a boil. Cook until potatoes are tender, about 10 minutes.  Stir in corn and mustard and cook until warm, 1 minute more. Season with salt and pepper to taste. Garnish with parsley and pickles before serving.