My mom used to make a potato leek soup alot while I was groing up and it was my favorite! I asked my mom for the recipe but she could not find it so I went on line and looked at a ton of defferent recipes and I took all the parts that sounded good to me and put them into one. And now this is mine and my moms new favorite. It is also yummy served cold.
prepare leeks by removing outer layer and dark green tops, wash, and cut into small pieces. chop onion into small pieces. prepare potatoes by pealling and cutting into small pieces, place in bowl of cold water till needed.
In a medium/larg saucepan over medium heat, melt the butter. Add the leeks,onion and a pinch of salt and sweat for 5 minutes. Add half of the broth and cook until the leeks are tender, approximately 15/20 minutes, stirring occasionally
Let leeks cool for a few minutes and transfer to blender, blend till desired smoothness (I like mine really smooth) Return to saucepan and add remaining broth and potatoes, cook till potatoes are very soft and broth/liquid thikens a little from the potatoes.
Just before serving add buttermilk, heavy cream, white pepper, and sour cream stir till well combined, leave on low heat just long enough to bring the temperature back up a little.
If desired when serving top with a spoon full of sour cream and some chives. Enjoy!