Start by thawing Greek yogurt or sour cream in a bowl while the frozen vegetables warm up. Chop russet potatoes into cubes and set aside for boiling.

Place the cubed potatoes in a large pot with cold, salted water. Bring to a boil over medium-high heat and cook for 20 minutes until tender. Drain the potatoes, reserving half for mashing later.

In a stockpot, heat your choice of ground meat over medium heat. Cook for 5-7 minutes until browned, draining any excess fat and seasoning with salt and pepper.

Add diced sweet onion, chopped celery, and minced garlic to the stockpot with the browned meat. Sauté for 5-6 minutes until onions are translucent and fragrant.

Stir in thawed mixed frozen vegetables and pour in chicken or beef bone broth. Bring to a soft boil, then reduce heat and simmer for 10 minutes, stirring occasionally.

Fold in reserved mashed potatoes and unmashed cubes into soup, stirring gently. Heat for another 5 minutes over low heat until thick and creamy.

Remove from heat, stir in thawed Greek yogurt or sour cream until fully integrated, achieving a velvety consistency.

Ladle the soup into bowls and garnish with freshly cracked pepper, chopped parsley, and sliced green onions.