Line 2 sheet pans with parchment paper or silicone baking mats.
In a small bowl, whisk together flour, baking soda and salt; set aside. In the bowl of a stand mixer, or a large mixing bowl, cream together the butter, shortening, granulated sugar, brown sugar, and vanilla on high speed until creamy and combined, about 2 minutes.
Add eggs and yolk, one at a time, mixing well after each addition. Stir in flour mixture on low speed or by hand. Do not over mix! Stir in chocolate chips/chunks.
Use a medium cookie scoop (2 Tablespoon size) to place 12 balls of dough on the pan, evenly spaced.
Bake for 9-10 minutes. Remove pans from oven and allow to stand for 2 minutes on baking sheet before transferring to wire racks to cool completely.
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