Chilled Beet Soup

• 1 Tbsp unsalted butter
• 1 Tbsp olive oil
• 1/2 yellow or white onion chopped
• 1 small potato peeled and chopped
• 1 carrot peeled and sliced
• 1 stalk celery sliced
• 3 medium beets peeled and chopped
• 4 cups chicken or vegetable stock
• salt
• Fresh cracked pepper
• Juice of 1/2 lemon
• 1 cup heavy cream Greek yogurt, half and half, or creme fraiche; use enough to bring out a bright fuchsia color in the soup.

for garnish

• a dollop of sour cream
• a sprig of mint or dill