Pre-heat oven to 180 degrees celsius, fan-forced.
Line baking trays with baking paper, greasing the corners first to prevent paper slipping.
Cream butter and sugar on med-high in a stand mixer.
Add egg and vanilla and beat again for a couple of minutes.
Fold in sifted flour, baking powder and custard powder.
Flour the kitchen bench. Separate dough into two parts and knead each until smooth.
Wrap dough in baking paper and place into the fridge for 15-30 minutes.
Separate the boiled lollies by colour. Place each colour bundle into a separate plastic bag and crush well using a rolling pin.
Once chilled, roll out pastry to a thickness of about 3mm making sure the bench you're working on is well floured.
Cut out cookies using medium cookie cutters. Cut out smaller shapes from the cookies using smaller cookie cutters. Use a spatula to transfer the cookies to the baking tray.
Bake for 5 minutes and then remove from oven. Carefully fill each small cutout section with the crushed boiled lollies. Return to the oven and bake for a further 5-7 minutes or until lollies have melted.
Allow to cool on trays for 10 minutes before removing cookies and placing on a cooling rack.