Melt the butter in a large pot over medium-high heat. Add in the onion and celery and cook until soft, about 4-5 minutes. Season with salt and pepper. Add in the garlic, smoked paprika, and Italian seasoning and stir together. Cook for another minute or until the garlic is fragrant.

Add the potatoes to the pot and sprinkle in the flour. Stir until you can no longer see and white flour streaks. Pour in the vegetable broth. Bring the soup to a boil, cover it partially with a lid and then lower the heat and let the soup simmer for about 20 minutes or until the potatoes are very soft.

Use a potato masher or immersion stick blender to mash the potatoes until the soup is your desired consistency. Stir in the milk, Greek yogurt, and cheese. Cook for several more minutes or until the soup is hot. Serve the soup topped with cheese, scallions, or your preferred toppings.