In a medium saucepan, combine four cups of water with the farro. Bring to a boil over high heat. Cover and simmer over medium-low heat until the farro is almost tender, about 20 minutes. Add salt and simmer until the farro is tender, about 10 minutes longer. Drain well. Transfer to a large bowl and let cool.
Saute squash until golden brown, season and set aside. Grill leeks until nicely charred, slice 1/2" thick on the bias. Roast peppers, peel, seed and roughly chop.
Once the farro has cooled, add the vegetables, Parmesan, and chives. Stir to combine.
In a small bowl, mix together the sherry vinegar, olive oil, mustard, pepper, and salt. Stir to combine. Pour the sherry vinaigrette over the farro salad. Toss to combine and serve.