Place bullion cubes in pot with six cups water (you can sub straight chicken broth for this if you prefer). Add turkey leg. Cover and bring to a boil, reduce heat and simmer thirty minutes. Turkey leg does not have to be covered with water/broth.
Place butter in large skillet over medium heat. Add onion, celery, and garlic. Saute until lightly browned.
Remove turkey leg from broth and dice up when cool. Add instant potatoes to broth and stir. Add onion mixture, beans, and diced turkey. Stir in salt and pepper. Bring to a boil, stirring constantly, and reduce heat to simmer for thirty minutes before serving.