Preheat oven to 170deg Celsius. Combine all ingredients (A) in a mixing bowl and beat on medium speed for 8-10 minutes, or until pale and fluffy. Pour into lined square baking tin and bake for 20 minutes. When baked, set aside to cool.
To make streusel: Whisk together all ingredients (B). Use clean hands to crumble the doughy banana mixture onto lined baking tray. Bake at 170deg Celsius for 8 minutes. Flip the crumbs and continue baking for another 10 minutes. Cool completely to harden
To whipped cream: Whip heavy cream in a completely dry and cold mixing bowl on high speed until soft peak. Add sugar and vanilla essence, continue beating until stiff peak. Spoon whipped cream into piping bag. Chill it for later.
To purée durian: Mash durian flesh with fork. Add heavy cream and sugar to combine well. Spoon durian purée into piping bag. Chill it for later.
To assemble the sweet treat: Use a cutter that fits your glass to cut out the layers of cake. Place a slice of cake layer. Pipe a layer of whipped cream, followed by a layer of durian purée. Top another layer of cake and repeat with whipped cream and duri
Tips: If you think the durian tastes sweet enough, omit sugar. If the texture of the durian you have is the wetter kind, omit the heavy cream. If you prefer to taste more of the original flavour of the durian, omit both sugar and heavy cream.
*Use a really cold mixer and bowl to whip the cream. Suggest placing the mixing equipment into freezer for at least 10 minutes before use.