Adjust your oven rack to the 2nd or 3rd level position (just above the center), preheat your oven to 350ºF, and line 2 baking sheets with either parchment paper or silicone baking mats.
In a medium-size mixing bowl, whisk together the all-purpose flour, cream of tartar, baking soda, and salt.
1 ¼ cup + 2 tablespoon All-Purpose Flour, 1 teaspoon Cream of Tartar, ½ teaspoon Baking Soda, ⅛ teaspoon Salt
Using your hand mixer or stand mixer fitted with the paddle attachment, beat together the vegetable shortening, unsalted butter, granulated sugar, and egg on medium-high speed.
¼ cup Vegetable Shortening, ¾ cup Granulated Sugar, 1 Large Egg, ¼ cup Unsalted Butter
Add in the whisked dry mixture and mix together until just combined.
Using a 1 tablespoon-size cookie scoop or spoon, scoop and shape the dough into 1-inch size balls. Roll in the cinnamon sugar mixture, then place on the prepared baking sheets.
Bake for 8-10 minutes at 350ºF. The cookies will puff up when baked, but will flatten as they cool. I recommend taking them out on the earlier side for a softer, chewier cookie. They should be golden brown on the edges, but look slightly under baked in the center
Transfer to a cookie sheet to allow the cookies to cool completely. Keep a slice of bread with the cookies in an airtight container to keep them nice and soft.
You can use ½ cup unsalted butter or ½ cup vegetable shortening (butter flavored or regular) instead of ¼ cup of each ingredient as shown above in the recipe.For a softer, chewier cookie, I recommend taking them out at the earlier recommended baking time. They might look slightly underbaked in the center, but they will continue to bake as they cool. For reference, I took mine out at the 8-minute mark.Recipe adapted from A Recipe Sampler by St. Andrew's Evangelical Lutheran Church.