Combine the farro, water and salt to taste in a saucepan and cook uncovered at a bare simmer until just tender, 20 to 25 minutes. Drain. There should be about about 2 cups. Spread the farro onto a platter to cool.

Toss together the farro, cheese, oil, pepper, and more salt to taste. Fold in the arugula, adding more oil as needed so the leaves are thoroughly coated.