In this tutorial, we learn how to make leek and potato soup. To make this, you will need: large leeks, onion, butter, vegetable stock, milk, salt, and pepper. First, cut up your leeks and place them into a pan and add in the butter. Make sure all the leeks are covered in butter while you are frying them. After this, add in salt and pepper, then cover and simmer for 10-15 minutes. Next, add in your vegetable stock and milk to the pan. Next add in mash to thicken up the mixture. After this, scoop up the soup and place it in a blender, then blend until smooth. When this is done, serve while hot and enjoy!