Preheat oven to 350 degrees and lightly grease a 11x7” baking dish with butter or non-stick spray, set aside.
Fill a large pot with water, add potatoes, and bring to a boil for ~5 minutes
Drain potatoes and run cold water over them to cool.
In a medium sized saucepan melt butter. Add in flour and milk, whisking until a thick roux is formed. Slowly add in beer, whisking as you do. Bring to a simmer.
Add cheese, continually stirring until melted and uniformly distributed. Season with a dash of salt and pepper.
In the prepared baking dish layer half of the potatoes, sausages and cheese sauce. Repeat layering with remaining half of each.
Cover baking dish with aluminum foil and bake for 15 minutes. Remove foil and bake for 5 more minutes.
Garnish with chives, serve warm.