Add macaroni noodles, water, butter, dry mustard, onion powder, seasoned salt, and pepper to the Instant Pot.
Seal the lid and select manual pressure high. Set the timer for 6 minutes. Manually release pressure once completed.
Do not drain the water in the bottom. Stir in cream cheese to melt. Add ¼ cup milk slowly until blended.
Stir in cheddar and parmesan. Add the remaining ½ cup milk, mixing a little at a time, until desired consistency is reached. You may not need all of the milk.
Prep remaining ingredients (shred cheese, etc.) while pasta cooks.
Refrigerate mac n cheese for 3-5 days in air tight, individual or meal sized portions. Freeze larger portions in an air tight container for up to 3 months.
Thaw mac and cheese in the refrigerator, then reheat covered in a 350°F oven for 20-30 minutes or until heated through. For individual portions, simply microwave at 15 second intervals, stirring in between, until heated.