Preheat oven to 350Â°F.
Whisk together the dry ingredients: flour, cream of tartar, baking soda, salt and cinnamon.
Cream together the butter, granulated sugar, and eggs thoroughly.
Slowly add the dry ingredients to butter mixture.
Pat dough into a ball and cover with plastic wrap. Chill for at least one hour.
Using a medium cookie scoop (about 2 tablespoons), make a ball of dough.
Flatten slightly in your hand and make a deeper hole in the middle.Place a caramel candy (two if using Milk Duds) in the hole and close the hole by pressing the cookie back into a ball.Make sure that the candy is completely enclosed in the cookie.
Optional: Roll the cookie in cinnamon sugar mixture.
Place cookie into the well of a [whoopie pie pan|http://www.amazon.com/gp/product/B004CYELQE/ref=asliss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B004CYELQE&linkCode=as2&tag=apesaisapee02-20]. Bake for 12 to 15 minutes.
Allow to cool in the pan and then remove by running a butter knife or spreader around the edge.