01 - 
                In a large pot, bring salted water to a boil and cook the pasta until al dente. Drain and set aside.
              
              
              
                02 - 
                In the same pot, melt the butter over medium-high heat. Whisk in the flour one tablespoon at a time. Cook until the mixture is thick, bubbly, and pale yellow.
              
              
              
                03 - 
                Gradually whisk in the milk and continue cooking until the mixture thickens into a creamy sauce. Season with salt, pepper, and red pepper flakes.
              
              
              
                04 - 
                Remove the pot from heat. Stir in the pepper jack and mozzarella cheese until melted and smooth.
              
              
              
                05 - 
                Return the drained pasta to the pot and mix well to coat all the noodles in the cheese sauce. Serve warm.