Stir the wholemeal shortbread biscuits with sugar, melted butter and grated ginger until everything is well mixed. Press the mixture onto the bottom of a cake pan or shallow bowl and place the pan in the refrigerator.
Boil the unopened can of condensed milk in a saucepan with water for 3 hours (once the water has boiled, you can put a lid on the saucepan and turn the stove down). Keep a close eye on the water to make sure the can is always covered with water. Then remove the can and let it cool for 10-15 minutes.
Open the jar and distribute the contents (toffee) on the biscuit base. Let cool, then spread the banana slices on the toffee. Whip the cream and spread on the bananas. Chill before serving.