Cut the cheeks from 1 mango, scoop the flesh from the cheeks and process until smooth, you will need 1/2 cup of puree. Add the chilled cream cheese and ¼ cup of the caster sugar, pulse until well combined (see tip).
Whisk the cream with remaining ¼ cup caster sugar and vanilla to form soft peaks. Add the sour cream and whisk until thick. Spoon about 3 tablespoons of the cream mixture down the centre of a 30cm long serving plate or board. Combine the coconut milk and rum in a shallow dish.
Dip one side of 2 biscuits into the coconut milk mixture. Sandwich together with 1 tablespoon of mango cheesecake mixture. Stand upright in the cream at one end of the plate/board. Working with one biscuit at a time, dip into coconut milk, then top with mango cheesecake mixture and sandwich against biscuits on the plate. Repeat to form a log-shape.
Spread the remaining whipped cream over the top and sides of log. Cover and refrigerate for 6 hours or overnight.
Before serving, remove the cheeks from the remaining mangoes. Carefully scoop out the flesh then thinly slice. Arrange the mango over the biscuit log and top with edible flowers. Cut diagonally into pieces and serve.