Scatter the sugar over a plate, then dip the cut sides of the peach halves into the sugar. Heat a frying pan over a medium-high heat and cook the sugared peach halves, cut-side down, until caramelised. Transfer the peach halves to a plate and carefully add the schnapps to the pan, if using, or a splash of water. Cook the liquid until reduced and syrupy, then return the peach halves to the pan and baste in the syrup. Remove the pan from the heat and leave to cool.

Beat the mascarpone and icing sugar together, then fold in the thyme leaves and double cream.

Divide the crumbled biscuits between two plates, then put one peach half on top of each bed of crumbs. Spoon the mascarpone cream onto the plates alongside the peach halves, then scatter over the frozen raspberries. Serve immediately while the raspberries are still frozen.