Boil a large pot of salted water, add ¾ pound pasta, and cook according to package instructions until al dente (about 8-10 minutes). Stir occasionally.

Melt 3 tablespoons of butter in a medium saucepan over medium heat for 1-2 minutes until foamy but not brown.

Whisk in 2 tablespoons of flour into the melted butter, cooking for about 2 minutes while stirring continuously until gently bubbling.

Gradually pour in 1 cup of milk while whisking to prevent lumps; cook for 3-4 minutes until thickened.

Stir in ½ to ¾ cup of pesto into the sauce, mixing well before removing from heat.

Drain cooked pasta and return to pot. Pour creamy pesto sauce over pasta and toss to coat evenly.

Serve immediately, garnishing with additional pesto, fresh herbs, or grated Parmesan as desired.