"Cream" of Vegetable Soup

This is a wonderful soup for fall.  I freeze some of the summer's bounty of zucchini and yellow squash so I'll have some for this soup after the warmth of the season has fled.

1 sweet onion, or a leek, peeled or cleaned and chopped
3 large carrots, chopped
4 Tablespoons butter (or olive or coconut oil)
2 pounds of potatoes, scrubbed and chopped.  I leave about half of the skins on.  I most often use Russets, but Yukon Golds or Red Potatoes are awesome.
2 quarts chicken broth
Several sprigs of fresh thyme tied together
4 summer squash (zucchini, yellow crookneck, etc.) sliced
Sea salt
Sour Cream or creme fraiche

Saute the onions or leeks and the carrots in the butter or oil until they are very soft.

Add the sauteed veggies to a stock pot, along with the chicken broth and potatoes, and bring to a boil.
Skim the foam and then reduce the heat and add the thyme sprigs.
Cover and cook until the potatoes are soft.
Add the summer squash and cook for another 10 minutes or so, until it is tender.

Remove the thyme.

Puree the soup with a stick blender.

Add water if the soup is too thick.

Season to taste.

Serve topped with sour cream or creme fraiche.