This is best made with corn stock which you can easily make after cutting the corn from the cobs. Combine the cobs in a large stockpot with some aromatics. I keep carrot, celery, mushroom stem, and onion scraps in the freezer for making stock and I just dumped a couple handfuls in with the box before covering with water. Simmer for a couple of hours, then strain and use the stock for the risotto. And note, while most rice dishes are made with a ratio of 2:1 for water:rice, the technique for making risotto requires much more liquid.