To cook the farro bring a large pot of lightly salted water to a rolling boil. Add the farro and cook for 20-30 minutes (taste every few minutes after the 20 minute mark). Once the farro is soft but still chewy, drain in a colander and fluff with a fork. Set aside.
In a large bowl toss together the cabbage, baby bok choy, cucumbers, scallions, and pistachios.
Combine all of the ingredients in a bowl and whisk together with a fork or small wish. Alternately, place all the ingredients in a lidded jar and shake until completely emulsified.
Add the room temperature farro to the cabbage salad, using kitchen tongs to combine. Drizzle the dressing over the salad, tossing until the cabbage is lightly coated (you might have leftovers).
Serve the farro and cabbage salad with an optional dollop of Greek yogurt and extra smashed pistachios.