1-Heat 1 teaspoon of cooking oil in a skillet over medium-high heat and brown the 6-8 ounces of kielbasa slices on both sides, then set aside.

2-In a large soup pot over medium heat, melt 4 tablespoons of butter. Add 1/4 cup diced onion, 1/2 carrot sliced into rounds and halved or quartered, and 1/3 celery stalk if using, and cook until the onion softens, about 3 minutes.

3-Stir in 3 tablespoons of all-purpose flour and cook for about 1 minute.

4-Add 2 cups of chicken broth or vegetable broth and 1 1/2 cups of milk, stirring well to combine.

5-Add 3 cups of Russet potatoes cut into 1/2-inch cubes to the pot and bring to a boil. Reduce heat to medium-low and simmer, stirring regularly, until potatoes and vegetables are tender, about 15-20 minutes.

6-Add the cooked kielbasa to the soup and cook for a few minutes to warm it through.

7-Stir in 1/4 cup of chopped fresh parsley or 1 tablespoon dried parsley.

8-Season with salt and freshly ground black pepper to taste.

9-Remove from heat and stir in 1/4 cup of shredded cheddar cheese or grated Parmesan cheese until melted. Serve garnished with additional parsley if desired.