In a large pot, melt the butter over medium heat. Add the chopped onion and minced garlic, cooking until the onion is translucent.

Stir in the flour to form a roux, cooking for an additional 2 minutes.

Gradually whisk in the chicken broth, ensuring there are no lumps, and bring the mixture to a simmer.

Reduce the heat to low and stir in the heavy cream, mixing well.

Add the chopped corned beef and drained sauerkraut to the pot, stirring until well combined.

Mix in the shredded Swiss cheese and Russian dressing, stirring until the cheese is melted and the soup is creamy.

Season with salt and black pepper to taste, adjusting as needed.

Simmer the soup for another 10 minutes, allowing the flavors to meld together.

Serve hot, garnished with rye bread croutons and chopped parsley.