Preheat the oven to 350℉
First prepare the cookie by combining the flour, coconut flakes, baking powder, salt & sugar together in a large mixing bowl
Add the melted vegan butter, oil & plant milk along with the vanilla extract
Mix everything together by hand with a spatula & the dough will seem slightly thick at first but then it will get glossy & more like a dough.
Scoop the dough with a 2 ounce scoop keeping them as round as possible & place them on a parchment lined sheet pan spaced 2" apart
Bake in the preheated oven for 15 minutes then using a tablespoon make an indent in the center of each one, return to the oven & bake for 3 more minutes
Cool while you prepare the custard by combining the sugar & cornstarch together then add to the plant milk in a small sauce pot over medium heat whisking constantly being the mixture to a boil
As soon as you see the first bubbles remove from the heat & continue whisking to a thick pudding consistency
Spoon the hot custard into each cookie indent allow to cool while you prepare the buttercream recipe
According to the instructions on that recipe post you will only prepare half recipe of the buttercream *and even this will be more than you need but the buttercream stores beautifully in the refrigerator for weeks or freezer for months
Once the custard is cooled & set pipe the buttercream on top of the custard on each cookie & then sprinkle a generous 1Tbs of toasted flaked coconut on top