Step 1

In a large saucepan, saute the onion and celery in butter until tender. Add broth and baking soda, and stir well. In a small bowl, whisk together the cornstarch and water until it becomes a smooth slurry, then gradually add the mixture to the pan. Bring everything to a boil. Cook and stir for two minutes or until the broth has thickened. Reduce the heat. Editor's Tip: A cornstarch slurry is a classic way to thicken sauce, soups and stews. Make sure the cornstarch and water are completely blended so you don't get lumps.

Step 2

Add the sauerkraut, half-and-half and corned beef to the broth mixture. Simmer and stir the soup for 15 minutes. Add the cheese, and heat until it's fully melted. Season with salt and pepper. Garnish with optional rye croutons.