You can bake or boil the potatoes. (Bake) Potatoes at 350 degrees for 65-75 minutes or until tender; cool completely. Peel and cube into 1" pieces. (Boil) Peel and cube the potatoes. Boil them, the yellow onions and celery in a large stockpot with the chicken stock until tender. If you don't have enough stock to cover the potatoes, add more stock. I use a 12 qt Non-Stick stockpot. In a large skillet, melt butter; stir in flour, salt and pepper (if desired) until smooth. Gradually add milk. Bring to a boil; cook and stir for 2 minutes until thickened. Pour into potatoes. If you want thicker soup, mash a few potatoes against the side of the pot and stir. Remove from heat; whisk in sour cream. Place back on stove, add Velveeta or American Cheese and Flavor Boost. Heat to serving temperature over medium heat, stirring occasionally. Ladle into bowl and garnish with bacon, cheese and green onions. Delish!!