For the Banana Espuma:
Bloom gelatin and blend with a small amount of the banana nectar over low heat until gelatin is melted. Combine with the remaining banana nectar. Strain into iSi whipper. Charge with two N2O chargers. Chill overnight.
For the Carbonated Raspberries:
Add raspberries to whipper and charge with two iSi CO2 soda chargers.
For the Chocolate Pudding Cocktail:
In a shaker with ice, combine cocoa bitters, raspberry syrup, rum, and chocolate pudding.
To Assemble and Serve:
Shake and strain into a sherbet glass. Top with banana espuma and carbonated raspberries.