Claire
Master Chef
I have used pistachios instead of pine nuts, with wonderful results. I do not like to substitute anything for basil, I just love the flavor. For cheese as far as I'm concerned it has to be a hard cheese with a lot of flavor. Parm or pecorino. The softer cheeses ... well, just cannot imagine it being the same. There is nothing wrong with the finished product, just call it something else. When you use cottage, ricotta, or mozzerella, you will wind up with something wonderful, but more appropriate to fill large shells, etc, with rather than something to put a dollop on a bowl of pasta (pesto as we know it ... well, a tablespoon will easily dress a bowl of pasta for two).