Wash spilt peas and remove any stones that may be present.
Soak split peas in 8cups cold water for 30 minutes before using. Drain water.
Combine split peas, chicken stock, cubed ham, chopped onion, and diced yam in Instant Pot. Secure lid. Pressure cook on high for 10 minutes. Do a quick steam release to release pressure. (I like to place a kitchen towel over the steam release to catch any liquid that may come out.)
Once steam has been released, carefully remove lid. Add garlic and onion powder, Italian seasoning, and salt and pepper to taste.
Secure lid on Instant Pot. Pressure cook on high for 2 minutes. Allow steam to release naturally. Remove lid.
Serve soup with a dollop of sour cream and croutons.