Pre-heat oven to 375˚.

Cook shells as per boxed instructions, drain and set aside.

In sauce pan or oven safe skillet, melt butter and add flour mixing until combined. Allow to cook for about 1 minute.

Slowly add in your Guinness and whisk until smooth, whisk in milk and allow to cook for 7-10 minutes allowing sauce to thicken.

Remove from heat and stir in cheddar until cheese is completely melted in, do the same with about half of your blue cheese crumble.

Add in pasta shells and stir until coated. Place in baking dish (if not using an oven safe skillet).

Melt butter for topping in a small pan, add in bread crumbs and stir. Cooking breadcrumbs until they are nicely toasted.

Sprinkle toasted breadcrumbs over mac n' cheese, and place in the oven and cook for about 25 minutes.

Sprinkle with a little more blue cheese and serve.