Potato Leek Soup

2 Tbs extra virgin olive oil
1 Tbs butter
2 large or 3 medium leeks (dark green parts removed), sliced crosswise (to yield 2 cups), washed and dried
1 small onion, diced
1 tsp sea salt; add more to taste
1 sprig fresh thyme
1/2 bay leaf
small pinch cayenne
4 cloves garlic, thinly sliced
12 oz. Yukon Gold or other medium starch potatoes, peeled and diced (to yield 2 cups)
4 cups chicken broth
2 Tbs minced fresh flat-leaf parsley
fresh ground black pepper to taste

Directions
In a heavy-based pot, heat the olive oil and  butter until hot. Add the leeks, onions and sea salt and then turn the heat to medium low. Add the thyme and bay leaf.
Cook slowly, stirring occasionally, until the vegetables are slightly softened, 10 to 15  minutes.
Add the cayenne and garlic. Cook, stirring for 1 minute, then
add the potatoes and chicken broth. Increase the heat and bring to a boil. Reduce the heat to a bare simmer, cover and cook until the potatoes are tender, about 15 minutes. Discard the thyme sprig and bay leaf.
Transfer 1 cup of the soup to a blender to puree and then return the puree to the pot.  Garnish with parsley and black pepper.