Add the elbow macaroni, water, 1 tablespoon of butter, and 1 teaspoon of salt to the inside of your Instant Pot. Stir well to ensure the macaroni is submerged under the water.

Place the lid on your Instant Pot and move the valve to "sealing".

Cook on high pressure for 4 minutes.

When the cook time is finished, hit the "cancel" button to turn the Instant Pot off. Carefully move the valve to "venting". Do a full manual pressure release.

Once the pin has dropped, indicating the pressure has been fully released, carefully remove the lid from the Instant Pot.

Stir the macaroni and drain in a colander in the sink. Place a bowl over the colander to keep the macaroni warm while you prepare the sauce.

Select the "Sauté" function and let the instant pot warm up.

Once the pot is warm, add the remaining 3 tablespoons of butter to the Instant Pot.

Once the butter is melted, add the flour and whisk well until all no dry flour remains.

Continue cooking, whisking often to prevent burning. You want to cook the "flour" taste out, and you are looking for a very light golden hue. You will need to cook and whisk for 2-3 minutes to achieve this, but it may be less time if your pot is particularly hot.

Once the roux has been sufficiently cooked, slowly pour in a small amount of the whole milk. Whisk to combine. This mixture will become very thick, very quickly. This is what will thicken your sauce. Whisk until it is lump free, then add more milk and whisk again. Repeat this until all the milk is gone and you have a lump free sauce.

Let the sauce cook until thickened, whisking frequently. This should take 1-3 minutes.

Add in the cubed processed cheese, and stir well to help it melt into the sauce.

Once the processed cheese is melted, add the cooked macaroni. Fold the macaroni in until it is completely covered in sauce.

Optionally, you may add ⅛ teaspoon (or more) of ground black pepper, and ½ tsp. dry ground mustard for a little extra flavor if desired. You may also season to your own particular tastes. Seasoned salt, paprika, and/or cayenne all make great additions if desired.

Serve macaroni immediately. This macaroni and cheese does not reheat very well, so I recommend serving it and eating it the day of preparation.