Chop up the celery into small chunks.
Chop up the onions (I used green onion because I'm intolerant to white onion but you can use whichever you prefer).
Chop up the potatoes into medium sized chunks.
Melt the butter in a large pot. Add the onions, celery, and potatoes and sauté on a medium heat for 5 minutes. The butter should look a bit creamy when it's done.
Add the salt and pepper. Add the white wine and reduce til it's about half it's quantity. Then add the stock and boiling water. Bring to the boils then turn down the heat and simmer for 20 minutes.
Check the potatoes are cooked through, they should break apart easily with a wooden spoon. Take off the heat and let it cool for at least 10 minutes.
Spoon the mixture into a blender and blend til smooth. If the mixture is too stiff add a bit more stock or water to smooth out.
Put the mixture back into the pot and the add milk. You can adjust thickness of the soup by adding more stock or water as desired. Gently warm the soup til it starts to bubble.
Season with salt and pepper to your liking and enjoy!