Minty Pea Soup

INGREDIENTS

• 3 unsalted butter
• 1 medium onion, chopped
• 4 low-sodium vegetable broth, divided
• 6 shelled fresh peas (from about 6 pounds pods) or frozen peas, thawed
• 1/4 fresh flat-leaf parsley leaves
• 1/4 fresh mint leaves
• Kosher salt, freshly ground pepper
• 1/4 crème fraîche or sour cream
• 2 heavy cream or water
• Chopped fresh chives (for serving)