Arugula Pesto

I love pesto!  And years ago when I started making it, I was a purist, making it with basil and pine nuts.  But pine nuts, as delicious as they are, are EXPENSIVE.  And basil was hard for me to find in large quantities.  So, I was very excited when I stumbled across a recipe for pesto that uses arugula and walnuts instead.
I feel like the Parmesan is difficult to replace, other than with maybe a Romano.  I’ve tried using cheddar when I’m out of the others, and it just doesn’t quite work.  I’ve also tried leaving the cheese out altogether.  And while it’s passable, it’s just not the same.  But the arugula and walnuts do truly work!  For me, anyway.  I’ve taken to just putting the ingredients in a bowl and using the immersion blender.  Then, I freeze leftover pesto in cubes and put them in a Pyrex for a later date.  
This is a very similar recipe to the one I use, although I only use 1/2 cup of olive oil.  I love to double it when I’m making it, so I have extra in the freezer.
Delicious on pasta, but also on quinoa or as a dip.  I’m sure many other possibilities as well.
Hope you enjoy!
NEW NOTE:  We were clean out of walnuts last time I went to make this.  I balked at my husband’s initial suggestion to use sunflower seeds instead, but it actually worked very well!  There are many recipes that do use sunflower seeds specifically with arugula, but I just used the recipe above and replaced the walnuts with sunflower seeds.  An even cheaper option, so I’m excited!