Cut the squash into 1cm thick slices in the shape of a half moon.
Heat some oil in a saucepan and fry the squash slices until they are golden brown on both sides. Place them on a plate lined with kitchen roll.
Add the onion to the same saucepan, adding a little more oil if necessary. Fill a glass with half vinegar and half water. Add the sugar and mix until the sugar has dissolved. Use lukewarm water to dissolve the sugar better.
Put the squash slices back in the saucepan and pour the vinegar, water and sugar mixture over the squash. Add some sultanas, cover with a lid and let it cook on low heat for a few minutes.
Put the squash slices on a plate and add a few mint or sage leaves and some pine nuts. Let it sit for a few hours before serving at room temperature. You can also serve this dish cold which would be great for a summer dinner.