Add the olive oil to a heated nonreactive rondeau. Add the onions, celery, and garlic. Cook until tender. Add the water and chicken base. Stir until base has dissolved. Add the farro. Bring to a boil. Allow to simmer over very low heat, stirring frequently. Keep covered between stirs. Cook until farro is cooked and has absorbed all of the liquid. If farro seems a little chewy, add a small amount of water, and cook until liquid has been absorbed. Season with salt and pepper, to taste. Place in a 2" (5 cm) full stainless-steel hotel pan. Allow to cool, uncovered. Transfer to a covered storage container and refrigerate until needed.