This was really good. I used cavatappi pasta. I substituted Guinness draught because I did not have the stout. I ended up using closer to 3 tablespoons of butter. I used Panko breadcrumbs. Next time I will mix the butter into the breadcrumbs and then sprinkle the crumbs over rather than trying to drizzle the butter evenly over the casserole. I think I will also up the cheese quantity just a bit. Thanks for posting.
My husband loves Guinness and I made this for St. Patrick's Day along with other recipes that called for Guinness. I'm very fond of my own mac and cheese recipe and don't drink beer so I was very hesitant to try this but I'm glad I did. This was so creamy. The Guinness flavor wasn't over powering and went very well with the cheeses.