When preparing the sauce, don't let it come to a boil. Continue whisking it over a constantly even heat. This will allow the cream/butter/flour mixture to gently thicken over the course of time. I prepared mine over medium/high heat, constantly whisking until thickness was just good enough to coat pasta.
KEYWORD creamy one pot pasta, creamy pasta recipe, creamy pasta with broccoli, easy broccoli pasta, easy pasta dinner