Preheat oven to 350 degrees. Position the rack to the middle of the oven.
In a large mixing bowl, whisk together flour, baking powder and salt. Set aside.
Using a stand mixer with the paddle attachment or a hand mixer, beat the butter and vegetable shortening until combined. Add sugar and beat until light and fluffy. Beat in eggs, one at a time, and vanilla extract until incorporated.
Turn the mixer on low and add the flour mixture. Beat until fully incorporated.
Gather dough into a disk, wrap in plastic or wax paper and refrigerate for 30-60 minutes.
Take the cookie dough out of the refrigerator. Cut the disk in half and let sit at room temperature for a few minutes. This will make it easier to roll out the dough. Place the other half back in the refrigerator.
Generously flour the board. Roll out disk to about 1/8-inch thick. Use a variety of Halloween cookie cutters to cut out shapes. Arrange cut outs on a baking sheet 2 inches apart.
Bake, one sheet at a time, for approximately 8-10 minutes, or until the cookies are just starting to turn golden brown on the bottom. (Cooking times may vary) Remove the baking sheet from the oven. Let the cookies cool on the sheet for about 2-3 minutes, then transfer to a wire rack and cool completely.
Gather any leftover scraps. Repeat the rolling, cutting and baking process. Once all the scraps are used repeat with the remaining dough.