Preheat the oven to 200C/180C Fan/Gas 6. Line 2 large baking trays.
In a large bowl/the bowl of a stand mixer combine the butter and both sugars on high for 3-5 minutes, until totally combined.
Add the vanilla and combine again, before folding in the flour, cream of tartar and baking soda.
Mix together the coffee and milk. Add into the dough and fold together until all combined and a cookie dough forms.
Combine the cinnamon and sugar in a small bowl. Take tbsp sized scoops of the dough, roll into a ball, roll in the cinnamon sugar and place on the baking trays. Spread apart at least 2 inches.
Press down each cookie a little before baking for 12-15 minutes, until golden brown at the edges. Let cool on a wire rack!