Spread the almonds in one layer on a silicone mat on a baking tray.
Heat the caster sugar and water in a small heavy-based saucepan over high heat for 6–8 minutes or until the sugar syrup turns a light caramel colour; do not stir. Add the butter and swirl the pan until the butter has melted. Immediately pour the caramel over the almonds to coat evenly. Set aside t