Step 1

Preheat oven to 350° Fahrenheit. In medium pot or saucepan, cook pasta according to package instructions, until al dente.

Step 2

Melt butter in large pot over medium heat, then add in flour and whisk until paste forms.

Step 3

Remove pot from heat. Slowly pour in milk, whisking constantly, and return pot to heat. Bring the mixture to boil before reducing to simmer. Simmer until sauce has thickened.

Step 4

Remove pot from heat again. Whisk in mozzarella cheese, cheddar cheese, and buffalo sauce. Return pot to heat and continue to whisk until cheese has melted.

Step 5

Remove cheese sauce from heat. Mix in shredded chicken, cooked pasta, and chopped celery. Transfer mixture to 9x13-inch baking dish.

Step 6

Top mac and cheese with crumbled blue cheese (if using). Place baking dish in oven and bake for 15-20 minutes or until lightly browned and bubbly. Serve warm.