Preheat the oven to 180C (356F). In a large bowl, add plantmilk, oil, sugar, vanillaextract and mix well together with a spatula until the sugar is dissolved.
Sift the two flours and the bakingpowder while adding them to the bowl with the liquids.
With a spatula, incorporate the flour and the liquids together trying to break the lump. Do not over-mix. It whould only take you 1 or 2 minutes.
Grease your springform pan with some vegetable oil, then dust it with flour and pour the cake batter in it.
Bake for 50 minutes at 180C (356F). Check with a toothpick if it's cooked inside.
Let cool down on a cooling rack before taking it out of the form and cutting it into 3 equal layers of about 2cm (0.8 inches) each. Use a serrated knife/bread knife to cut the cake.
For the custard
In a pot off the heat, whisk together all the ingredients for the custard till there are no lumps in the liquid.
Bring onto the heat, and keep whisking, on low-med heat, until the liquid truns into a thick custard. Then take off the heat and let cool down for 20 min, stirring occasionally.
For the syrup
In a small pot on low heat, dissolve the sugar in the water, then add the vanilla and set aside.
Assembling the cake
Place the base layer of the sponge cake onto a serving platter and brush it with ⅓ of the syrup.
Cover it with a generous amount of coconut custard.
Put the middle layer of sponge cake on top of the custard, applying some gentle pressure to fix it in place. Brush another ⅓ of the syrup on top, and cover with another layer of custard.
Add the last piece of the sponge cake on top of the custard, but flip it upside down. Then with a spatula level off the custard coming out on the side of the cake.
Brush the top layer with the remaining syrup, then cover the whole cake with your vegan whipped cream.