Instant Pot is the easiest way to cook boxed Kraft macaroni n cheese! You don't even need to drain it! Dump box contents into the Instant pot, add water, butter and milk and press the button!
Put macaroni and water in the Instant Pot. Close the lid and turn the vent to a Sealing position. Press the "Pressure Cook" or "Manual" button and set the time to 2 minutes on High pressure.
When it's done cooking, let the pressure release naturally (NR) for 5 minutes, then quick release (QR) the remaining steam.
Open the Instant Pot and add milk, butter and the contents of the cheese packet. Mix the macaroni and cheese with a spoon so the cheese powder turns into sauce and the sauce is evenly distributed.
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Notes
You can cook several boxes of mac n cheese at once. If using multiple boxes, add just enough water to cover the macaroni.