Instructions

1. Sort the raspberries first and throw out any with grey fuzz. One mouldy berry taints the whole blender, and you will not see it once it is puree.
2. Blend the berries with the sugar and the lemon juice, then leave the mixture to stand for ten minutes. The sugar needs that time to dissolve, and undissolved crystals end up as gritty patches in the sheet.
3. Push half the puree through a fine sieve and stir it back in if you want a smoother result. Straining all of it takes out so much seed that the leather loses its grain, which is most of the character of a raspberry one.
4. Line the tray with baking paper rather than trusting a bare mesh. This mixture is thin enough to run straight through a mesh insert before it has a chance to set.
5. Pour it on and tilt the tray until it flows level, keeping the layer shallow. A deep pour on a short run leaves a sheet that is dry at the rim and still liquid under the skin in the middle.
6. Dehydrate at 60 °C for 4 hours, and treat that as a minimum rather than a target. Raspberries carry more water than almost anything else you would make a leather from.
7. It is done when the surface no longer feels sticky and the sheet lifts away from the baking paper without stretching. If it stretches, lay it back down and look again in an hour.
8. Cut it cold with a sharp knife, roll the strips in baking paper, and keep them in a sealed container for a month at room temperature or three in the freezer. The sugar helps it keep, but a roll that weeps at the ends was still wet in the middle when it came off.