1. Set aside some of the blackberries for garnish (about 12). Place the remaining blackberries, wine, cassis, lemon juice and peel, cinnamon and sugar in a large, shallow saucepan and heat gently until the sugar has dissolved.
2. Meanwhile, peel the apples neatly, cut in half and carefully remove the cores with a teaspoon or melon baller. Place the apples, cut side up, in the poaching liquid, cover with a lid and simmer very gently for 15 minutes or until the apples are just tender. Baste frequently with a spoon. Take the pan off the heat and leave the apples to cool in the poaching liquid for several hours, at least, basting from time to time as they cool.
3. Carefully remove the apples to a plate and sieve the syrup into a clean saucepan, discarding the solids. Boil the sauce until reduced to a thick syrup, about 5-7 minutes then leave to cool.
4. When ready to serve, lay two apple halves on individual dessert plates, spoon over the sauce and garnish with the reserved fresh blackberries.