Preheat the oven to 375 F.

In a mixing bowl, add butter and sugar then mix well.

Add the eggs and milk then mix again.

In another bowl, add flour, cornstarch, baking powder, baking soda, salt, cinnamon and cream of tartar then mix together.

Add the flour mixture into the butter mixture then mix until a dough forms.

Mix in the cinnamon chips (if using) and then scoop into large balls, for extra large cookies aim for ~3 inch cookie dough balls (it will make between 12-14 extra large dough balls).

In a medium bowl, add and mix together the sugar and cinnamon.

Add the cookie dough balls into the cinnamon sugar mixture and roll around so they are well coated.

Place cookies onto a lined cookie sheet and sprinkle the tops with more cinnamon sugar mixture.

Bake for 12-13 minutes. If you want a gooey cookie; bake for 11-12 minutes.

For regular sized cookies, roll into ~1 1/2 inch dough balls and bake 7-8 minutes.