In a 6-quart Dutch oven, brown the ground beef; then set aside.
Chop the onion, carrots, and celery; then add to the Dutch oven. Add the dried basil, parsley flakes, garlic powder, salt, pepper, and 2-tablespoons of butter. Cook over medium heat for 10 minutes until the vegetables (especially the carrots!) are tender. Dice the potatoes while the veggies are cooking, making sure to stir the vegetables occasionally.
Add the chicken broth and diced potatoes. Bring to a boil, then reduce heat, cover, and allow it to simmer for 10-15 minutes, or until the potatoes are tender.
Melt the remaining butter in a separate small saucepan and add the flour. Stir and cook for about 3-5 minutes or until thick and bubbly. Pour the flour and melted butter mixture into the pot of soup. Stir and cook for another 2 minutes.
Reduce the heat to low and add the shredded American and Monterey jack cheese, and milk. Cook until the cheese melts. Finally, mix in the sour cream and pickle juice, if adding it, then serve!