How to Make It
In a large saucepan, heat 2 tablespoons of the oil. Add the onion, carrot, celery and rosemary; cook over high heat, stirring, until just softened. Add the farro and cook, stirring for 1 minute. Add the stock, water and a pinch of salt; bring to a boil. Cook over moderately high heat, stirring occasionally, until the farro is tender, 15 minutes. Drain the farro, reserving 1/4 cup of the cooking liquid. Discard the rosemary sprig.
Meanwhile, pour 1 inch of water into a large skillet and bring to a boil. Add the broccoli rabe and cook over high heat until just wilted. Drain the broccoli rabe well, then coarsely chop.
In the skillet, melt the butter in the remaining 2 tablespoons of oil. Add the scallions, shallot and broccoli rabe. Season with salt and pepper; cook over moderately high heat until tender, 2 to 3 minutes. Add the farro and its reserved liquid; cook, stirring until heated through. Stir in the vinegar, grapes and pecans. Season with salt and pepper, transfer to a bowl and serve.