What are the intricate tips for making a custard cake?

I am going to give you some tips for preparing a custard cake. Preheat the oven upto 180 degree Celsius. Then you have to grease a 18cm x 28cm Pyrex dish with butter and set it aside. First make the custard. Stir that custard powder, sugar and little milk over low or moderate heat on the stove until that custard thickens and coats the back of a spoon. Set it aside. In a very large mixing bowl, just cream the butter and sugar. Add some eggs one at a time. Fold through a sifted flour and then the custard powder alternately with the milk. Put half of that mixture into that greased Pyrex dish. Spoon the warm custard on the top. Add the rest of the cake mixture on the top, placing a little mounds here and there. Bake at 180 degrees for about 40 minutes. Then cool in that Pyrex dish and sprinkle with icing sugar.