Creamy potato soup

6 cups peeled, diced Russet potatoes

1 1/2 cups chopped yellow onion

1 1/4 cups peeled, diced carrots

1 cup diced celery

2 (14.5 ounces each) cans low-sodium chicken broth

Salt and pepper

1/3 cup butter

1/3 cup all-purpose flour

2 1/2 cups milk

1/2 cup sour cream

Optional toppings: chopped bacon or ham, shredded cheddar cheese, chopped green onions or chives

Combine diced potatoes, carrots, celery and onions with chicken broth in a large pot and season to taste with salt and pepper. Cover pot and bring to a boil over medium-high heat. Once it reaches a boil, reduce heat to medium and continue to cook 15-20 minutes longer, until potatoes are very soft when pierced with a fork. In a medium sauce pan, melt butter over medium heat, add flour and cook for 1 minute while whisking constantly. While whisking, slowly add milk and cook, stirring constantly until mixture begins to thicken. Once potatoes are soft, add thickened milk mixture to potato soup mixture and stir. Add sour cream and mix well. Top each serving with desired toppings.