Using a small, sharp knife, score an X 3 cm long into one end of the peaches, barely cutting into the flesh - this will help you peel it later. Place the ginger, lemongrass, chilli, lime leaves, lime juice, honey and 150 g of the sugar into a pot wide enough to hold all the peaches in one layer - don’t crowd them. Add 2 litres of water. Bring to the boil then simmer for 10 minutes. Gently drop the peaches in off a slotted spoon and bring back to a rapid simmer. Place a cartouche on top of the peaches and poach until cooked - you should be able to poke a toothpick into the centre easily. From time to time, give them a tumble to help them cook evenly. Once they’re cooked, turn the heat off, carefully take them out of the liquid and plunge into a bowl of icy water. Leave for a few minutes then peel the skin from them and return to the still hot liquid and leave to cool in it. Once cooled they can be kept covered in the fridge for 5-6 days, so long as they float in their liquid.
Reserve a dozen cashews and split them in half, then roughly chop the remainder. Place the remaining 50 g of sugar in a heavy-based pan and place over a moderate heat. Cook until it melts and then turns golden brown. You can stir it gently once it begins to melt, but go gently or it can caramelise. If nothing is happening to the sugar turn the heat up until it does. Stir in the chopped nuts then tip onto a baking tray lined with non-stick paper, spread it out, being careful not to burn yourself with the hot caramel, and leave it to go cold. Carefully pour a litre of hot water into the pot and leave it to simmer for a few minutes - this helps when it comes time to clean it. Once the cashew caramel has cooled and set, break it up by bashing with a rolling pin or similar and mix into the mascarpone. Then mix in the cream and stir briskly to incorporate it all.