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 until bubbly. Gradually whisk in the flour, cooking each addition until fully incorporated and the mixture is thick and pale yellow.
03 -
Slowly add the milk while whisking continuously until the sauce thickens and becomes creamy.
04 -
Season with salt, pepper, and a pinch of red pepper flakes. Remove from heat and stir in the shredded cheeses until fully melted and smooth.
05 -
Return the drained pasta to the pot, stirring until evenly coated with the cheese sauce.