Heat oven to 350 degrees.
Spray a casserole dish with cooking spray.
Cook pasta according to directions; drain and set aside.
In Dutch oven stockpot over medium heat, melt butter. Slowly add flour, continuously whisking. Whisk in chicken broth. Slowly add cream, whisking throughout. Gradually add 3/4 cup of each of the four cheeses while continuing to whisk until smooth.
Add pasta to cheese sauce, stirring to mix well. Turn into the casserole dish and spread evenly. Add the remaining cheese on top. Sprinkle crumbled bacon over cheese.
Bake 15 minutes.