Add the farro, one onion half, garlic, a handful of parsley and salt along with 2 3/4 cups water to a 2-quart pot. Bring to a boil, then cover, reduce to a simmer, and cook for 10 minutes. Turn off the burner and let sit, covered, for 5 more minutes. Discard the onion, garlic and large pieces of parsley. Spread out on a rimmed sheet pan and let cool completely (do not skip this step or the mozzarella will melt into the finished dish).
Whisk together the olive oil, vinegar, and honey to prepare the dressing. Chop the remaining onion half finely. Add onion, cooled farro, mozzarella, kalamata olives, tomatoes, remaining tablespoon of parsley and basil to a deep bowl. Pour the dressing over the ingredients and stir well to combine, using a long wooden spoon or rubber spatula. Season with salt and pepper. The salad is ready to serve, but can also be made and stored in the fridge, covered, one day ahead.