Microwave the milk and vanilla seeds together in a large heat-proof bowl for 3-4 minutes.

Meanwhile, crumble the biscuits into thumb-nail size pieces and use to generously cover the base and sides of a 23cm diameter shallow tart plate.

Beat the eggs and sugar thoroughly together. Add both flours. Add this mixture into the hot milk, return it to the microwave and cook for 10 minutes, whisking regularly to ensure a smooth thick sauce.

Pour the sauce gently and evenly over the biscuits to fill the tart plate.

Set aside to cool down to room temperature, sprinkle generously with ground cinnamon and refrigerate until firm enough to slice into wedges.