Minimalist's Potato Leek Soup

We were having a relatively mild winter but recently, it's been getting pretty cold and I've been craving soup.  I've never made potato leek soup before but I recently decided that I love leeks (and potatoes aren't too shabby either).  This soup led to a lot of surprises:

1. So easy
2. Way more flavorful than you'd expect with such a short and simple ingredient list
3. Not all potato soup recipes are heavy and creamy (this was a surprise to me, at least)
4. Pretty, pretty, pretty filling

I thought I had chicken broth when I started this recipe but quickly realized the chicken broth I had in the fridge was most likely not ok to consume (i.e. I smelled it...).  I added Greek yogurt (magical of magical ingredients) to give the soup a creamier texture without the heaviness of cheese or, you know, cream.  This is also delicious with a nice hunk of crusty bread and a side of carb coma. Enjoy!

Minimalist's Potato Leek Soup
Ingredients

1 leek, quartered and chopped (only white and pale green parts)
1 teaspoon butter
3 cups potatoes peeled and chopped into 1/2 inch pieces (about 2 large russets)
2 cups water (or broth, if you're fancy)
1/2 cup 2% Greek yogurt
dried thyme
salt
pepper
fresh chives to garnish (optional)

Preparation
Cook the leeks in butter with salt and pepper in a medium sized sauce pan. Cover the pan and cook on low heat until softened. Make sure not to brown leeks as it will cause them to have a burnt taste.

Add water and potatoes.  Bring to a low simmer and cook for about 20 minutes. Scoop about two thirds of the soup mixture (less if you want it chunkier) into a blender or cusinart along with the Greek yogurt and puree.  Return to pan. Add thyme and more salt and pepper to taste.  Garnish with fresh chives.