Yes! However, you'll need to add a few other ingredients to mimic the flavour and colour of custard. At the beginning of cooking, I recommend adding a pinch of turmeric (for colour) and, if you like, black salt (for an eggy flavour). Turmeric's colour intensifies as you cook it so try to not add too much. I also recommend increasing the sugar to 1 cup (200g). For extra richness and flavour, you can also add soy or coconut milk powder, to taste. I don't recommend using tapioca starch as it will make the custard slimy.