I finally got my hands on the family recipe for "forcer cookies". They're custard cookies made using a cookie press, also known as a cookie forcer. I just had to take a million photos because they're super cute!
Here you can see my cookie press, which is very modern...
And a 1970s (I think) model which my aunty bought on ebay:
This 1970s model is very similar to the one my aunty uses, which she bought in 1973 for $4.50. My cookie press was a present, but I'm guessing they cost a fair bit more than $4.50 these days.
You can see how the range of aluminium shapes compares with the vintage selection on the left, and the selection for the modern model on the right:
And you can see the shapes I tried out this time...
I can't share my recipe because it's a family secret. But there are lots of great recipes out there for custard cookies. I recommend googling "cookie recipe custard powder" or similar. And custard cookies taste best when made into little sandwiches with vanilla icing as the filling.
Now it must be time for a cup of tea and a custard cookie!