In a medium-sized mixing bowl, sift or whisk the 1 teaspoon baking soda, 1 teaspoon cream of tartar , 1/2 teaspoon salt and 4 cups all-purpose flour
In a large mixing bowl or the bowl of a stand mixer, cream together the 1 cup unsalted butter, 1/4 cup shortening, 1 cup granulated sugar and 1 cup brown sugar, until light and fluffy.
Add in the 2 large eggs, beaten, followed by the 1 teaspoon vanilla extract
Add in the sifted dry ingredients, followed by the 6 butter brickle candy bars (such as Heath bars), crumbled.
Form dough into logs, around 2" in diameter. Wrap logs of dough in either plastic wrap or parchment paper. Refrigerate overnight (or freeze if not planning to bake right away).
Slice dough 1/4" thick; place on lined baking sheet and bake @350°F 10-12 minutes (increase baking time by 2 minutes if baking from frozen state). * Cool cookies on wire rack and store in airtight container.