In a small bowl, whisk together flour, baking soda, and salt. Set aside.
In a large bowl, beat together butter and shortening until well-combined.
Add sugars, and beat for about 4-5 minutes on high, or until very well-combined.
Add eggs, one at a time, and vanilla; beat in for 3 minutes.
Stir in flour mixture until just combined.
Add chocolate chips or chunks, and stir in.
Cover, and refrigerate dough for at least 2 hours.
Preheat oven to 375, and line 2 baking sheets with parchment paper.
Drop dough by medium scoops (1.5 tablespoons) onto prepared cookie sheets.
Bake for about 8-10 minutes, or until very lightly browned at the edges.
Remove from oven, and let cool on baking sheet.