For the almond crumb, add the sugar to a saucepan and place over a medium heat. When the sugar starts to melt and turn to a liquid around the edges, slightly shake the pan but do not stir. Leave until about a quarter of the sugar has melted and then slowly stir the pan until all the sugar is melted and a caramel forms. Stir in the almonds and then pour on to a baking tray lined with baking paper. Leave to cool completely then crack and blitz the mixture to a crumb.
For the amaretto semifreddo, beat the egg whites in a bowl, gradually adding the sugar until stiff peaks form. In a separate bowl, whip the cream, vanilla seeds and amaretto until the cream forms soft peaks. Fold the two mixtures together and then stir in the almond crumb. Spoon into six individual cling film-lined small dessert moulds. Leave in the freezer for a few hours to set.
For the roasted peaches, preheat the oven to 190C/170C Fan/Gas 5. Heat the butter and vanilla seeds in a saucepan. Stir in the sugar and amaretto. Add the peaches and baste in the melted butter for a few minutes. Place the peaches in a small roasting tin and spoon the liquor over. Roast in the oven for 20–25 minutes, basting the peaches every now and then, until the peaches are golden brown and caramelised and the liquor has almost reduced to a syrup.
Serve the peaches alongside the semifreddos.