Once the chicken has been cooked and set aside to rest, continue to heat the cast-iron skillet on high with about 2 tablespoons of chicken fat coating the bottom. For a vegan alternative, heat up 2 tablespoons of olive oil. Add the cooked farro in a single, even layer and cook undisturbed until it puffs up and begins to brown, 2–3 minutes. Drizzle with olive oil, stir, and add the Brussels sprouts leaves, along with a big pinch of salt, pepper, and the sliced garlic. Stir again and and cook until the Brussels sprouts begin to wilt, about 1–2 minutes. Turn off the heat, add the lemon juice, and finish with a drizzle of olive oil.
You can make this dish in the same pan as Chef Gillespie's Cast-Iron Skillet Chicken.