In a large skillet over medium-high heat, brown the ground beef for 5–7 minutes until fully cooked, breaking it into small pieces. Drain excess grease.

Transfer the cooked ground beef to the slow cooker and add diced tomatoes, chopped white onion, diced celery, and diced russet potatoes. Pour in beef broth, Dijon mustard, nutritional yeast, dried parsley, and season with salt and pepper. Stir to combine.

Cover and cook on high for 3–4 hours or on low for 6–8 hours until vegetables are fork-tender.

About 30 minutes before serving, steam the remaining diced russet potatoes with water until fork-tender. Drain and blend with almond milk until smooth.

Stir the creamy potato mixture into the slow cooker, mixing well to combine. Adjust seasoning if needed.

Ladle the soup into bowls and top with chopped dill pickles and fresh shredded lettuce. Serve immediately.