01 - Bring a large pot of salted water to a boil. Cook pasta until al dente. Reserve 1/2 cup pasta cooking water before draining.
02 - Place avocados, spinach, garlic, olive oil, milk, Parmesan, lemon juice, salt, black pepper, and red pepper flakes in a blender.
03 - Blend until completely smooth and creamy. Add reserved pasta water if sauce is too thick.
04 - Return drained pasta to the pot. Pour sauce over pasta and toss gently to coat, adding more pasta water as needed for silky texture.
05 - Serve immediately garnished with extra Parmesan, fresh basil, and toasted pine nuts.