1.Combine sugar, juice, water and rind in a medium saucepan. Stir over low heat 1-2 minutes, until sugar dissolves. Add the berries. Simmer, uncovered, 35 minutes until berries soften.
2.Meanwhile, in a medium bowl, combine cream, icing sugar and vanilla. Using an electric mixer, beat until soft peaks form. Gently fold into mascarpone.
3.Toast brioche lightly. Serve brioche topped with warm berry compote and mascarpone cream.
Be careful not to over-beat the mascarpone cream mixture, as it may split.