Place all ingredients into the Instant Pot. Ensure the steam valve is on “Sealing,” select "High Pressure," and set the timer to cook for 5 minutes.
Wait at least 15 minutes to open the lid. Release any residual pressure by carefully moving the steam valve to “venting.” Residual pressure will release. Now, safely open the lid.
Remove the stainless steel insert from the machine. Use an immersion blender, and blend until smooth. Alternately, use a regular blender to puree the soup. (Use caution when blending hot soup in a blender. It needs a steam vent, or the heat pressurize the lid, and it will spray.)
Add all ingredients to a large pot and simmer for at least 30 minutes. You might need to add extra water to compensate for evaporation. The soup is done when the onions are soft, and everything is well cooked.
See the instructions in Step 3 above and blend into a smooth puree.
Coconut milk often curdles when boiled. Do not worry if you see this. After you blend the soup it will become homogenous again. Thanks to Food52 for publishing the recipe that inspired mine. It is by Urvashi Pitra.