Combine broth and seasonings in your Instant Pot and whisk together. Stir in the elbow macaroni.
Place lid on Instant Pot and set to sealing. Cook on manual function on high pressure for 5 minutes. When done, do a quick release.
There may be a small amount of liquid left in the pot, do not drain. Immediately stir butter and all three cheeses into the hot macaroni. Continue stirring until the cheeses are completely melted.
Stir milk into the macaroni gradually until loosened and creamy.