In a large pot over medium heat, melt the butter. Add the chopped onion and minced garlic, and sauté until soft and translucent, about 5 minutes.

Sprinkle in the all-purpose flour, whisking to combine. Cook this mixture for about 2 minutes until it turns a light golden color.

Gradually pour in the chicken broth, whisking vigorously to eliminate clumps. Increase the heat slightly to bring to a gentle simmer, about 5 minutes.

Reduce heat to low, and stir in the heavy cream until fully combined.

Add the chopped corned beef and drained sauerkraut, stirring well and letting meld for about 5 minutes.

Sprinkle in the shredded Swiss cheese and the dressing, stirring until the cheese is melted.

Season the soup with salt and pepper to taste.

Let the soup simmer on low for an additional 10 minutes, stirring occasionally.

Serve the soup garnished with the rye bread croutons and chopped parsley.