Place the Creamy Sauce ingredients in a blender and puree until smooth. Adjust salt to your taste.

Heat oil in a large skillet over medium high heat. Add garlic and cook for 20 seconds, then add onion and cook for 3 to 5 minutes until translucent and cooked through.

Meanwhile, cook your pasta of choice in a large pot of salted boiling water until al dente (just cooked through but still firm). SCOOP out 1 mug of the pasta cooking water, then drain the pasta.

Add the pasta into the skillet, then pour the Creamy Sauce in, all the spinach and about 1/2 cup of the pasta water (Note 5). Stir to coat the pasta in the sauce and to wilt the spinach. Cook, stirring gently, for about 2 minutes until the sauce is warmed through. Adjust salt to taste.

Use the remaining pasta water to get the sauce to the consistency you want.

Remove from the stove and serve immediately, with more parmesan cheese and basil if desired.