Bring a pot of salted water to a boil. Cook the macaroni noodles, drain, and mix with butter. In a large pot over medium heat, mix the cream, cream cheese, mustard powder, and beer. When the mixture is smooth, whisk in the cheddar and pepper jack. The cheese mixture can come to a light simmer but should never boil. Add the pasta to the cheese. Warm through and place in a serving dish.