Toss the brown butter with the butternut squash. Roast the squash in a 425 degree F oven until just tender and brown on the edges, 10 to 15 minutes. Meanwhile, cook the farro in boiling, salted water, until just tender (a slight chewiness is desirable in farro), about 10 minutes. Drain the farro, toss with olive oil and season lightly with salt and pepper. Set aside.
Combine the cranberries, brown sugar, vinegar, cinnamon, allspice and orange zest and juice in a saucepan. Cook over medium heat until the cranberries are bursting and their juices have slightly thickened, about 15 minutes.
When you are ready to serve the salad, place the farro in a large serving platter, scatter the roasted squash, mint, arugula and feta over top. Drizzle with the cranberry vinaigrette and some olive oil.