Preheat the oven to gas mark 3 or 170 degrees.
Add the egg, plain flour, cornflour and baking powder and mix well until it forms a dough.
Mix the chocolate and funfetti into the cookie dough ensuring they are spread throughout.
Form small balls of cookie dough (slightly smaller than golf balls) place on a lined baking tray. I almost made them like vertical cones to ensure they didn't spread too much. Leave space between each cookie just in case.
Make sure a few funfetti is exposed on the surface so that they show through after baking (I rolled the cookie ball into a little funfetti before baking)
Bake for 12-15 minutes or until golden.
Leave to cool on the baking tray to firm up.