Preheat oven to 180oC.
Combine the flour, corn flour, cocoa powder and baking soda in a large bowl.
With an electric mixer, beat together the butter and sugar. Then gradually add in the milk until combined.
Add the flour mixture 1⁄2 at a time to the butter mixture until all is combined.
Fold in the chopped pistachios.
Roll out your cookies and place on a lined baking tray – you can make these as big or little as you like.
Bake for 10 minutes checking along the way. For gooey cookies check at 8 minutes.
Once the cookies have cooled completely on a wire rack, melt the dark chocolate and drizzle over the top.
For added crunch sprinkle the cookies with extra crushed pistachios.