Bring a large pot of salted water to a rolling boil over high heat. Once boiling, add about ¾ pound of your favorite pasta. Cook according to package instructions, typically 8-10 minutes, until al dente, stirring occasionally to prevent sticking. Reserve ½ cup of pasta water, then drain the pasta and set it aside in the pot.

In a medium saucepan, melt 2 tablespoons of butter over medium heat until bubbly, which should take about 1-2 minutes. Sprinkle in 2 tablespoons of flour, whisking continuously to create a smooth roux. Cook for 2-3 minutes, letting it bubble gently, which helps to remove any raw flour taste.

Slowly pour in 1 cup of milk while whisking constantly to prevent lumps. Increase the heat to medium-high and continue stirring until the sauce thickens, approximately 3-5 minutes.

Remove the saucepan from heat and stir in ½ to ¾ cup of pesto, depending on your flavor preference. Mix well, ensuring the vibrant green sauce incorporates fully into your creamy mixture.

Return the drained pasta to the pot and pour the creamy pesto sauce over it. Toss everything gently to ensure each piece of pasta is enveloped in that luscious sauce.

Garnish your creamy pesto pasta with your choice of toppings, such as grated Parmesan cheese, fresh spinach, or cooked proteins like chicken or shrimp. Serve immediately.