Press the button SAUTÉ. Set it to "Normal" and heat one tablespoon of oil.
Add onion, celery, and lemongrass into the pot and cook until tender for about 2-3 minutes. Stirring occasionally.
Add basil leaves, frozen peas and give them a quick stir for about 10 seconds.
Add broth into the pot, stir for about 10 seconds. Lock the lid onto the pot.
Press SOUP or Pressure Cook (Manual) on High pressure for 12 minutes with the Keep Warm setting off. The valve must be closed.
Use the quick-release method to bring the pot’s pressure back to normal. Unlatch the lid and open the cooker.
Remove the lemongrass stalks from the soup and stir in the coconut milk. Adjust seasoning with salt and pepper if needed.
Transfer the pea soup into a high-speed blender. Puree the soup in 2 batches until very smooth.