Set your Instant Pot to sauté mode and heat the oil. Add the chopped onion and minced garlic, sautéing until fragrant and softened, about 3-4 minutes.
Add the shredded cooked chicken to the pot, stirring to combine with the onion and garlic.
Next, add the finely chopped cabbage to the pot, followed by the chicken broth. Stir everything together until well combined.
Close the Instant Pot lid and set the valve to sealing position. Cook on manual high pressure for 5 minutes.
While the Instant Pot is cooking, prepare the creamy sauce. In a separate bowl, mix together the skim milk and cornstarch until smooth.
Once the cooking time is complete, perform a quick pressure release. Carefully open the lid and stir in the milk-cornstarch mixture and cottage cheese until well combined.
Allow the mixture to simmer for an additional 2-3 minutes on the sauté mode, stirring occasionally, to ensure the cornstarch is fully cooked and the sauce has thickened to the desired consistency.
Season the chicken cabbage mixture with salt and pepper to taste, adjusting seasoning as needed. Serve the Instant Pot Chicken Cabbage hot, garnished with a sprinkle of chopped parsley or green onions if desired.