Preheat oven to 180 °C / 160 °C (fan); grease/line a container (25 x 22 x 4 cm)
Cream together butter and sugar till light and fluffy
Beat eggs and gradually add into batter. Also add vanilla.
Fold in flour and coconut.
Add milk.
Bake 25-30 min, till done.
Mix jam to soften then spread over the surface of the cake and top with the rest of the desiccated coconut.
Cut into squares, serve with custard.
Notes
Original link also contains instructions on making your own custard. seems a faff
made this immediately AFTER uploading, which is the opposite way round to how i usually do, and it took (is taking, at time of writing) over double the time to bake it should have and the top was kind of overdone. Recommend cooking at 180+ even on fan? Or perhaps just don't use a pyrex dish