Boil penne pasta in salted water until al dente; reserve 0.25 cup pasta water and drain.
In a blender jar, place fresh basil leaves, garlic paste, cashews, parmesan cheese, salt, and black pepper.
Pulse while slowly drizzling olive oil until a vibrant green pesto sauce forms.
Transfer warm cooked pasta into a serving bowl and fold in the prepared basil pesto.
Add a splash of reserved pasta water if needed to loosen, toss well, and serve immediately.