This one is simple: a no-bake (stove-top & fridge), veganised vanilla slice.
Packet of plain square vegan crackers
(e.g. Jacob's cream crackers)
Vegan custard made up as follows:
4 tbsp custard powder (Bird's and Orgran are vegan and have no artificial colourings)
2 tbsp sugar
1 pint (about 568 ml) plant milk (I used soy).
(Basically it's an ordinary vegan custard but made with double measure of powder, so that it's thicker)
A cup or so of icing sugar. You can either mix it with passionfruit pulp & juice to the right, spreadable consistency, or use a little plant milk plus a drop of lemon extract -- something slightly tangy or acidic to offset the thickness of the filling.
Place one layer of crackers in the base of a deep-sided rectangular tray. You may have to bevel the corners to make them fit; you can see I also used some thinner strips at the edges. On a pyrex dish, I didn't need to grease the base.
Place in fridge to set and chill. The longer you can leave it, the better the crackers will soften. Using the crackers is a lower-fat approach than using pastry (and no baking involved), and you virtually can't taste the difference.