Begin by trimming the leeks,using only the white parts and some of the lighter green as well.Be sure to rinse and clean the leeks well,they tend to hold sand or dirt in the rings of the leek.I slice them and put them in a large bowl of cold water to soak,then rinse and repeat as needed.
Saute the onion,garlic,leeks and spices in the olive oil until soft,5-10 minutes.Add the chicken stock,2% milk,diced russet potatoes and bring to a simmer for 20-25 minutes.Puree the soup with an immersion blender or food processor in batches being careful not to burn yourself.
Melt the butter with the flour and add the the soup to thicken,serve with fresh chopped chives or dill. You can also serve with a spoonful of sharp crumbled Tilsit blue cheese if desired. Enjoy!! :)