Using the saute mode, heat the electric pressure cooker until “hot.” Add the ground beef and onion, cooking until the beef is browned and crumbled. Drain well. Cancel the saute mode.
Meanwhile, in a large bowl, whisk together the garlic, dry mustard, worcestershire sauce, tomato paste, and beef broth.
Return the beef to the pressure cooker and and top with elbow macaroni. Pour the beef broth mixture over the macaroni. Do not stir.
Place the lid on the electric pressure cooker and set the valve to sealing. Set the pressure cooker to “manual” or “pressure cook” for 5 minutes. Quick release the pressure when the cook cycle is complete.
Stir the sour cream and cheese into the pasta.
Serve topped with additional cheese or garnished with fresh parsley.