Melt butter in a large pot over medium high heat. Add onions, carrots and celery, Saute for 8 to 10 minutes, until softened.
Add water, potatoes, chicken noodle soup mix, garlic powder, chicken bouillon, ground beef and pepper. Stir together. Bring to a boil. Reduce heat to medium low. Cover and simmer for 30 minutes.
Remove from heat. Stir in Velveeta cheese, milk and sour cream. Garnish with parsley.