Bring one 455g can crushed pineapple in juice or syrup to boil (use two cans if you want a richer filling – one crushed, one pieces).
Thicken with 3T custard powder mixed to a paste with 1/4c water.
In a food processor,
cream 125g butter, 3/4c sugar,
add 1 egg and sifted 1/4c cornflour,
1 1/2c flour and 1t baking powder.
Remove half the dough and press into a shallow sponge roll tin and spread with cooled pineapple filling.
Add extra 1/4c flour (approx) to remaining dough and pulse until mixture crumbles.
Sprinkle over pineapple filling, pressing down gently. Bake for 25-30 min at 180c.
When cooked, dust with icing sugar, serve warm or cold with cream or ice-cream.