Preheat the slow cooker if necessary; see the manufacturer's instructions. Pour the apple juice into a small saucepan, add the sugar, saffron and cardamom pods and their tiny black seeds. Bring to the boil, then tip into the slow cooker pot.
Cut each pear in half lengthways, leaving the stalk on, then cut away the skin. Remove the pear cores with a melon baller, if you have one, or a teaspoon. Add the pears to the slow cooker pot, pressing them beneath the surface of the liquid as much as you can. Cover with the lid and cook on low for 3–4 hours or until the pears are tender and pale yellow.
When ready to serve, put all the ingredients for the sauce into a small saucepan and warm together, stirring until smooth. Spoon the pears and some of the saffron sauce into shallow dishes, pour the chocolate sauce into a small jug and allow dinner guests to drizzle the sauce over the pears just before eating. Complete with a spoonful of ice cream or crème fraîche, if liked.