01 -
Bring a large pot of salted water to a rolling boil. Add pasta and cook according to package instructions until al dente. Reserve some pasta water if desired, then drain.
02 -
Melt butter in a medium saucepan over medium heat. Whisk in flour and cook, stirring constantly, for 2 minutes to eliminate raw flour taste.
03 -
Gradually whisk in milk, increasing heat to medium-high. Cook until sauce thickens and coats the back of a spoon, then season with salt.
04 -
Stir pesto into the sauce until fully combined. Remove from heat. Adjust thickness with reserved pasta water or milk if necessary.
05 -
Return drained pasta to the pot. Pour over creamy pesto sauce and toss thoroughly to coat evenly.
06 -
Divide pasta among plates and serve immediately. Optionally, add cooked protein, fresh spinach, sun-dried tomatoes, or cheese before serving.