Turn pressure cooker to the "sauté" setting. Melt butter (3 tablespoons) and sauté onion, celery, and carrots, seasoned with salt and pepper to taste, for about 5 minutes, until softened.
Add the split peas, chicken stock (6 cups), ham bone (or hock or 6 oz. diced cooked ham), and the 2 bay leaves.
Cover pressure cooker and set to manual, high pressure for 15 minutes.
Allow the pressure to naturally release for 10-15 minutes.
If you used a ham bone or hock: remove the it from the soup and remove the ham meat that's still attached to it. Add the ham meat back into the soup.
Taste and adjust seasonings if necessary. Serve immediately, or store in your refrigerator for up to 1 week or freezer in an airtight container for up to 6 months.
If you want to use a frozen ham bone, you shouldn't need to adjust the cooking time, since ham bones are technically already cooked, you're just reheating it! Keep in mind though, the colder your ingredients are, the longer it will take to come to pressure.
For a vegetarian version, omit the ham, use more salt and pepper, and make sure to use vegetable stock or water instead of chicken. For a vegan version, use olive oil instead of butter.
If you don't eat pork, you can substitute the ham bone for a smoked turkey leg.
To make this in your slow cooker, add all ingredients (omitting the butter) to slow cooker and cook on low for 8 hours or high for 4 hours, or until split peas are cooked to desired tenderness.
To make this on your stovetop, sauté veggies as instructed in a large pot. After adding the remaining ingredients, bring to a boil, cover, and simmer for approximately one hour (or until split peas are cooked to desired tenderness).
This soup will likely thicken once it cools and is refrigerated, especially if you use a ham bone to make it because of the gelatin. Thin out with water and adjust seasonings as necessary.
I made this recipe in my 6 qt. Instant pot. It should work the same in an 8 qt., but you may need to cut the ingredients in half for a 3 qt. mini. You should also be able to double the batch in an 8 quart pressure cooker.
The provided nutrition information does not include any added sodium from seasoning to taste, any optional ingredients, and it does not take brands into account. Feel free to calculate it yourself using this calculator or by adding the recipe to Yummly.