Sieve whole wheat flour, custard powder, salt, baking powder and baking soda in a bowl. (Dry mixture)

In another bowl, mix sugar and oil until well blended and creamy.

Add one cup orange juice to the sugar and oil mixture and mix well. (Liquid mixture)

Incorporate liquid mixture into the dry mixture and add orange zest and mix very well until no lumps are there.

Pour the batter in a greased cake tin. Tap the pan so that air bubbles are released.

Now mix handful of all-purpose flour and chocolate chips until well coated in a small bowl. And topple over the cake.

Bake the cake in a preheated oven at 180℃ for 25-30 minutes or as needed.