Start by bringing a large pot of salted water to a boil. When it reaches a rolling boil, add your pasta and cook according to the package instructions until al dente.

While your pasta is cooking, melt the butter in a medium-sized saucepan over medium heat. Once melted, whisk in the flour until smooth. Cook for about two minutes while stirring constantly. Slowly add in the milk, continuing to whisk over medium-high heat until your sauce thickens.

Once your white sauce has thickened nicely, stir in the pesto until fully incorporated. Remove from heat.

Drain your cooked pasta but remember to reserve some of that starchy water if needed later! Return the drained pasta back into its pot and mix in any additional cooked proteins or veggies if desired.

Pour the creamy pesto sauce over the pasta and gently toss until every noodle is coated. Serve immediately while hot.