In the bowl of a stand mixer fitted with a paddle attachment or a large bowl, beat together butter, sugar, and brown sugar until light and fluffy.
Beat in the eggs, then the vanilla extract.
Add the flour, cream of tartar, baking soda, and salt. Mix until just combined with no streaks of flour remaining.
Fold in the thinly chopped chocolate until evenly distributed.
Cover the dough and refrigerate for about an hour until well chilled.
Preheat oven to 375˚F (190˚C). Line two baking sheets with parchment or lightly grease.
In a wide bowl, mix together sugar and cinnamon to make the topping.
Use a small cookie scoop or spoon to take out heaping tablespoons of the chilled dough and form into balls.
Roll each ball thoroughly in the cinnamon sugar and place on the prepared baking sheets 2 inches (5 centimeters) apart.
Bake in preheated oven until just set, 10-13 minutes.
Allow to cool on the baking sheets for 10 minutes before removing to wire racks to cool to room temperature.
Store in an airtight container at room temperature for up to three days.