Set your Instant Pot to the sauté function and heat the oil, butter, or bacon fat.
Add the diced onion, chopped celery, and diced carrots to the Instant Pot. Sauté for 5 minutes or until the vegetables are slightly softened.
Stir in the minced garlic and salt, and cook for an another minute.
Add the split peas, stock or water, bay leaves, and fresh thyme (if using) to the Instant Pot.
Secure the lid and set the Instant Pot to manual high pressure for 15 minutes.
Once the cooking time is complete, allow for a natural release of pressure for 10 minutes, then use the quick release for any remaining pressure.
Remove the bay leaves and thyme sprigs from the soup. Use an immersion blender or a regular blender to puree the soup to your desired consistency.
If using chopped ham, stir it into the soup after blending.
Season with cracked black pepper and adjust salt to taste.
Serve it piping hot!