Remove cheese packet from box. Add water to instant pot insert (1.25 cups for a 6 oz box like Annie's, 1.5 cups for a 7.25 oz box like Kraft) and pour pasta in. Push pasta into water if need to create an even layer, but do not stir.
Close pressure cooker and set valve to sealing. Turn on high pressure for 3 minutes (elbows) or 4 minutes (shells). Quick release pressure for al dente noodles, allow 1-2 minutes for a natural release for a softer bite.
Add the cheese powder, milk, and butter to the pasta and stir until well combined. Serve warm.
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Notes
Water needed is ¼ cup per oz of dry pasta.Milk and butter amounts may vary with the box- ingredients here are for a 6 oz box of Annie's shells.Milk can be added to the water before cooking the pasta, or with the cheese powder after.
Nutrition information is provided as a courtesy and is an estimate. It is recommended to use your preferred calculator with the actual ingredients you use for optimal accuracy.