Add the condensed milk, golden syrup and white chocolate and stir until everything is just melted and combined. Remove from the heat and allow to cool a little.
Place the cornflakes in a bowl and roughly scrunch with your hands to make slightly smaller flakes, but not dust.
Add them to the pan together with the oats.
Sift in the custard powder, flour and bicarb of soda.
Mix well then roll tablespoonfuls into a ball with your hands and place on lined baking trays. I put 8 on each 23 x 30 cm tray and had 36 balls all together.
Flatten each ball slightly and press a few crushed cornflakes onto the tops.
Bake at 180℃ (350℉, Gas 4) for 10 minutes or until golden and crunchy looking on the top.
Slide onto a rack to cool.
Notes
Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.