Preheat oven to 180°C.
Soak the raisins in warm water.
Sift the chestnut flour and salt in a large bowl. Add the water in a thin stream, stirring continuously to avoid lumps. Continue to add the water until you have a smooth and liquid batter, autumnal brown and warm. It is supposed to be as liquid as a pancake batter. Add half of the pine nuts and half of the well squeezed raisins and stir again.
Grease with extra virgin olive oil a rectangular baking-pan, about 25 x 40 cm large, and scrape in the chestnut batter.
Sprinkle with the remaining pine nuts and raisins the surface and add the rosemary needles.
Drizzle with extra virgin olive oil and bake for about 35 minutes until the chestnut cake is firm and covered with wrinkles, crisp on the outside and soft inside. You can eat it warm or cold.