Place a large pot or Dutch oven over medium-high heat. Add the lean ground beef and cook until it is fully browned. Use a wooden spoon to break the meat into small crumbles. Drain any excess fat if necessary.

Add the diced onion, carrots, and celery to the pot with the beef. Cook for 5 to 7 minutes, stirring occasionally, until the vegetables begin to soften.

Stir in the minced garlic, tomato paste, dried thyme, and dried rosemary. Cook for another 2 minutes until the garlic is fragrant and the tomato paste darkens slightly.

Pour in the beef broth and soy sauce. Add the cubed potatoes to the pot. Stir well to combine all ingredients.

Bring the mixture to a gentle boil. Once boiling, reduce the heat to low and cover the pot with a lid. Let it simmer for 15 to 20 minutes, or until the potatoes are fork-tender.

Take a potato masher or a large spoon and lightly crush a few of the potato chunks against the side of the pot. This releases starch and naturally thickens the soup.

Stir in the frozen peas and cook for 2 more minutes until they are bright green and heated through.

Remove the pot from the heat. Stir in the Greek yogurt until it is fully incorporated and the soup looks creamy.

Season with salt and black pepper to taste. Garnish with fresh parsley before serving.