Melt unsalted butter over medium heat, add chopped onion and minced garlic, sauté for 5 minutes until the onion is translucent.

Stir in all-purpose flour, cooking for 2 minutes while whisking to avoid lumps.

Gradually whisk in chicken broth, bring to a simmer and thicken.

Lower heat, stir in heavy cream until blended into a smooth texture.

Mix in chopped corned beef and sauerkraut, heat through for 5 minutes.

Stir in shredded Swiss cheese and dressing until cheese is melted.

Season with salt and pepper to taste.

Let soup simmer on low for 10 minutes, then serve hot, garnished with croutons and parsley.