Heat olive oil in the pressure cooker, using the BROWN setting. Add onion and brown until soft. Add cauliflower, stock, and half and half. Cover, set to high pressure, and set timer for 10 minutes.
Let the pressure drop using the quick-release method. Unlock and remove lid. The cauliflower should be very soft. If it's still hard, cook under pressure for an additional 2-3 minutes, or until tender.
Puree the soup in batches in a blender until smooth. Pour back in the pressure cooker. Season with salt and pepper. Stir in parsley and mint.
Recipe courtesy of Deni, Reprinted with permission.