Stir juice, 240gm sugar and 250ml water in a saucepan over medium-high heat until sugar dissolves, bring to the boil, then transfer to a sieve lined with muslin placed over a deep bowl and leave to strain (1-2 hours; don’t press the pulp). Meanwhile, soften 5 gelatine leaves in a bowl of cold water (5 minutes). Transfer strained juice mixture to a saucepan (discard pulp) and warm over medium-high heat, squeeze excess water from gelatine, add to pan, stir to dissolve then strain into a 1.75-litre mould and refrigerate until set (3-4 hours).
Soften remaining gelatine in a bowl of cold water (5 minutes). Bring milk, rind and remaining sugar to a simmer in a saucepan over medium-high heat, stirring to dissolve sugar, then remove from heat. Squeeze excess water from gelatine, add to pan and stir to dissolve, then add buttermilk and whisk to combine. Cool slightly, then pour onto set blood orange jelly and refrigerate to set (overnight).
Combine orange segments, strawberries, raspberries and moscato in a bowl with icing sugar and stand for 10 minutes to macerate.
To serve, briefly dip mould into a large bowl of hot water, then loosen around the sides by gently pulling jelly with a finger to break the vacuum. Place a serving plate on top of mould and invert. Carefully remove mould and serve with blood orange and raspberry salad.