Very Green Broccoli Soup

Ingredients

• 1 1/2 pounds broccoli
• 2 tablespoon extra-virgin olive oil
• 1 tablespoon unsalted butter
• 2 tablespoon minced garlic
• 1 cup diced onion (1/4-inch pieces)
• 1/2 cup diced celery (1/4-inch pieces)
• salt
• freshly ground black pepper
• 2 teaspoon finely chopped fresh thyme leaves
• 5 cup chicken stock (or canned low-salt chicken broth)
• 2 cup packed spinach
• 2 teaspoon freshly grated lemon zest
• 1 cup heavy cream or buttermilk (if using buttermilk, cut the lemon zest in half)