First make the pasta per manufacturers instructions for ‘al dente” in a large pot.
While the pasta cooks, add the butter to a large heavy saucepan.
Melt the butter over medium heat.
Add the flour and stir well.
Cook over medium low heat for 2-3 minutes stirring constantly, until bubbly and thickened.
Slowly add the milk, stirring constantly to prevent lumps.
Increase heat to medium and simmer for about 5-10 minutes until the sauce is thick and creamy.
Add the salt and shredded cheese.
Stir until the sauce is smooth and the cheese is completely melted.
Remove from the heat.
Drain the pasta and add back into the large pot.
Add to the cheese sauce to the pasta.
Gently fold in and allow to sit for about 3 minutes.
Serve immediately or keep warm in a slow cooker.