1Put 5g (or a teaspoon) of the butter in a small microwavable bowl or cup with the chocolate.
2Beat remaining butter until it is creamy (soften in the microwave for 20 seconds if its hard). Add sugar slowly & cream together (about 3 minutes).
3Microwave the chocolate until soft or melted (about a minute) then beat into the butter sugar mix, followed by the egg & vanilla essence.
4Sift in flour, cocoa, salt, baking soda & cream of tartar & beat to combine.
5In a small bowl or cup, combine the extra sugar & cinnamon.
6Use a 1 Tablespoon measure to scoop out dough & roll into balls then roll them in the sugar/cinnamon mix to thoroughly coat.
Place balls on a lined baking sheet, 2" apart to allow for spreading.
Do not flatten.
7Bake at 180C for 8-10 minutes.
Leave to cool on the tray & they will firm up.