Melt butter and golden syrup in a heavy pot on the stove.
Add cocoa powder and stir until smooth and incorporated.
Pour in cornflakes. Make sure all cornflakes are covered with the syrup mixture.*
Line cupcake tin with liners and plop equal parts of sugary cornflakes in each liner.
Cool in the refrigerator at least 30 minutes before eating.
We started with 4 cups of cornflakes and ended up adding another cup and a half. It all depends on your personal preference.