Bring water to a boil in a large stockpot. Add the elbow macaroni and cook according to package directions.
Meanwhile, in a large 10-inch cast iron skillet, add olive oil, ground beef, shallot, salt and pepper. Cook for about five minutes or until the beef is no longer pink.
Add the flour and stir until incorporated, about a minute. Stir in beer and bring to a slight boil. Keep stirring until thicken about 3 to 4 minutes.
Remove the skillet from the heat and stir in milk and cheese until melted and well incorporated.
Add the drained pasta to the skillet and mix into an even layer.
Preheat the broiler. Sprinkle shredded cheese over the top of the Guinness mac and cheese.
Place skillet under broiler for about 5 minutes or until golden brown and bubbly. Remove skillet from broiler and serve immediately with a big glass of Guinness.