Preheat oven to 170ºC. Butter and flour a 16cm cake pan (with removable base if available.) Set aside.
To make cake batter, place sugar into Thermomix bowl and mill 10 sec/speed 10.
Add butter, and banana and blend 10 sec/speed 4.
Add remaining cake ingredients and blend 10 sec/speed 6. Scrape down sides of bowl and blend 5 sec/speed 6.
Spread batter into prepared cake tin and bake 40-45 minutes until inserted skewer comes out clean.
Pierce entire cake several times through to almost the base, stopping 1 cm from the bottom of the cake. The more holes you create, the better.
To make the Tres Leches Syrup place the milks and vanilla into a clean Thermomix bowl and cook 5 min/90ºC/speed 2. Pour this hot syrup over the pierced cake slowly so that the holes absorb the liquid. Make more holes if necessary. The moisture of the dessert depends on the cake soaking up this syrup. Cool completely. If you cannot add any more, reserve remaining syrup for service.
Remove cake from tin.
To make Caramel Bananas, peel bananas and slice.
Place remaining ingredients into a flat fry pan and cook on a medium heat (Induction 6) until bubbling and blended. Add sliced bananas and just heat through.
Slice the cake into wedges. Top with Caramel bananas, and toasted coconut if using. Serve with additional Tres Leches Syrup and whipped cream, to really tip you over the edge….a dessert not for the faint hearted!!