In a medium pot, add the cornstarch/cornflour and 1/2 cup of the milk and whisk until there are no lumps and it is well combined. Add the remaining milk and whisk until smooth. Place on medium heat and add the sugar. Cook, whisking or stirring constantly, until it thickens into a custard, 7 to 8 minutes. Add the vanilla and pandan and stir until combined.

In a medium dish - mine was a 2.75 quart / 2.5 liter Pyrex dish that measured 8 inch x 6 inch x 3 inch high - place a layer of custard (you will need 4 layers of custard so use about 1/4 of it). Top with cookies, bananas, and then dollop with yoghurt (no need to spread it out) and custard. Repeat these layers 2 more times, finishing with a layer of custard. Cover and refrigerate for at least four hours or overnight.

When ready to eat, scoop into bowls. Scatter more crushed cookies on top and serve cold.