"doesn't taste like celery, my lily-white ass": celery root & apple soup

Ingredients

• 1 tablespoon unsalted butter
• 4 cups 1/2-inch cubes peeled celery root (from one - 1 1/4-pound celery root)
• 3 cups 1/2-inch cubes peeled cored Granny Smith apples (from about 2 medium)
• 1 1/2 cups chopped onion (about 1 large)
• 1/4 cup white wine
• 4 cups low-salt chicken broth
• 4 sprigs of thyme
• 1/4 cup buttermilk
• fine-grain sea salt and fresh-cracked black pepper, to taste
• 1/4 cup snipped chives, for garnish
• extra-virgin olive oil, for drizzling