Add the mint leaves to a Collins glass and lightly muddle.
Add the cognac, liqueur, syrup, lemon juice and 3 dashes of the bitters, and swizzle until diluted.
Fill the rest of the glass with crushed ice.
Add the 3 remaining dashes of bitters, then garnish with a mint sprig, lemon wheel and sliced bananas.
*Demerara syrup: Combine 2 parts demerara sugar to 1 part water in a saucepan over low heat. Heat until the sugar dissolves. Cool before using.