In a large 5-7 quart pot, like this one, over medium heat, add the butter, onions, and potatoes. Stir together and cook for 5 minutes, stirring every couple minutes. Add the garlic, salt, pepper, white pepper, Italian seasoning, rosemary and bay leaves. Let these cook together for another 5 minutes.

Turn up to high heat and stir in the chicken stock, gently scraping up the brown bits from the bottom of the pot. Bring it up to a boil and let boil for 5 minutes. Then, reduce the heat to medium and stir in the beans. Let cook for another 5 minutes.

To the blender, add the milk and the soup mixture, or use an immersion blender. You may need to do this in batches depending on the size of your blender. Blend on high until velvety and smooth. Pour the soup back into the pot, give it a stir and a taste. Add additional salt and pepper, as needed. Serve warm with a sprinkle of fresh rosemary and toasted bread (or croutons!)

Leftovers keep well in the refrigerator for up to 1 week. To reheat, simply pour into a pot over medium heat and cook until warm, or use the microwave. Soup freezes well up to 3 months.