Preheat oven to 325 degrees F and grease a 9x13 baking dish and set aside
Prepare pasta according to box instructions. Keep the pasta a little more al dente as you will be baking it as well
In a separate large pot melt the butter, add flour, and whisk until the mixture turns golden brown
Add milk and continue whisking until the mixture thickens
Add cheese, salt, and pepper, and whisk until melted and fully incorporated
Add cooked pasta to the cheese mixture and stir until combined and cheese is evenly distributed
It's at this point you can stir in any add-ins you might want - like cooked bacon, mushrooms, cooked lobster - of course this dish is delicious even with no add-ins!
Pour mixture into prepared baking dish and pop into the oven for 20-25 minutes until cheese is bubbly
Serve on its own in a big 'ole bowl or as a side dish - and enjoy!