Press sauté to preheat the Instant Pot. When the word 'hot' appears on the display, add the olive oil, then the onion, celery and carrots. Cook, stirring occasionally, until the onion is soft, about 5 minutes. Press cancel to turn off the Instant Pot.
Add the chicken stock, taking care to scrape up any browned bits from the bottom of the pot. Add the ham bone, split peas and bay leaf.
Secure the lid with the steam vent in the sealed position. Press soup and immediately adjust the timer to 20 minutes. Check that the display light is beneath high pressure.
Once the timer sounds, allow the pressure to release naturally for 10 minutes, then quick release the pressure and carefully remove the lid.
Remove the ham bone and any meat that fell from the ham bone from the pot. Remove and discard the bay leaf.
Using an immersion blender, puree the soup until smooth.
Remove the meat from the ham bone and add it and any other meat that was removed back to the pot.
Season well with salt and pepper, then serve.
