In a blending cup, mix the oats with all the other ingredients up to and including the salt. Transfer the mixture to the prepared tin. Flatten the base by hand and create a rim of approx. 2 cm around the edge with your fingers. Place a sheet of baking paper over the base, weigh down with dried pulses (e.g. lentils).
To blind bake
Approx. 15 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, leave to cool, remove the baking paper and pulses.
Bring the plums and sugar to the boil while stirring, reduce the heat and simmer for approx. 5 mins. Using a whisk, stir in the cornflour and all the other ingredients up to and including the cinnamon, bring to the boil while stirring, simmer for approx. 1 min., allow to cool slightly. Spread the plum layer onto the base, leave to cool.
Combine the coconut milk with all the other ingredients up to and including the vanilla paste, bring to the boil while stirring with a whisk. Allow to cool slightly, pour on top of the plum layer, leave to cool. Cover the cake and chill for approx. 5 hrs.
Decorate the cake with the jam and plums.