Heat 1 tablespoon of the oil in a large, heavy-based saucepan, add the wheatberries and spices and toss well to coat. Pour in the stock and bring to the boil, stirring constantly. Cover with a tight-fitting lid, remove from the heat and leave to stand for 25 minutes until all the liquid is absorbed and the grain is tender.
Meanwhile, heat the remaining oil in a heavy-based frying pan, add the aubergine cubes and cook over a medium-high heat, turning occasionally, for 4–5 minutes until golden all over and tender. Add the walnuts and toss over the heat for 1 minute.
Transfer the wheatberries to a large bowl and toss with the lemon rind, aubergine and walnuts, then leave to cool for a few minutes before adding the spinach and coriander leaves. Toss well and season with a little salt and plenty of pepper, then serve with lemon wedges.