Try making authentic Italian red sauce. It's easier and tastes incredible. You can use cilantro/spinach as a substitution for basil. This recipe is good but I don't like the flavor of milk combined with spices. It masks the tang I like.
For your kind info Italians use onion to make white sauce which is obtained from a mixture of Milk and parmesan and 1 onion is use to reduce the lactose level of the milk