Add 12 ounces dried macaroni or elbow pasta, 2 cups reduced-sodium chicken broth, 1 cup water, 3 tablespoons butter, ½ teaspoon salt, ½ teaspoon garlic powder, ¼ teaspoon onion powder, ¼ teaspoon mustard powder, and ¼ teaspoon ground black pepper to the inner pot of the Instant Pot. Press the pasta gently with a spoon to submerge it, but don't mix it.
Secure the lid and set the valve to sealing. Manually set to pressure cook for 4 minutes.
Once the timer goes off and beeps, release pressure immediately by carefully turning the valve from sealing to venting. Let all the pressure release and open the lid.
You'll see a little residual liquid in the pot, which is normal. Mix in ½ cup heavy cream and 3 cups shredded cheddar in batches till you get a smooth, creamy sauce. Serve immediately.