Spread the almonds on a silicone mat on a baking tray.
Blanch the orange zest in a pan of simmering water for 10 seconds, then drain. Set aside.
Heat the water and caster sugar in a small heavy-based saucepan over medium heat. Cook for 6 minutes or until the sugar syrup reaches a light caramel colour. Immediately add the butter and drained orange zest an