In a large pot, melt the butter over medium heat. Add onion and celery, cooking until softened, then stir in garlic for one minute.

Sprinkle in flour and stir constantly for about a minute to form a roux, which prevents lumps and thickens the soup.

Gradually whisk in broth, then add diced potatoes. Bring to a simmer, cover, and cook until potatoes are tender, about 15–20 minutes.

Use an immersion blender for a smooth texture or mash half the potatoes in the pot for a chunkier feel.

Lower the heat and stir in milk and cream, warming gently without boiling to avoid curdling.

Season with salt and pepper, then remove from heat. Let the soup rest for 5 minutes to let flavors meld.

Ladle into bowls and top with crispy bacon, chopped chives, or shredded cheese for extra flair.