Holy cow! Why haven't I tried this before?
Gustavo loves pesto, but our basil plant is not very robust...and it kills me to spend $4 on a tiny amount of fresh basil at the store. Spinach, though, well we always have a bag of that on hand.
So this is a few handfuls of spinach, two large garlic cloves, sea salt, pine nuts, parmesan and a healthy glug or two of olive oil. Yum. It does have that spinach taste, and would probably be better with basil mixed in, but in a pinch, its a nice inexpensive pesto.