When ready to bake, preheat oven to 325°F and line two baking sheets with parchment paper. Set aside.
In a small bowl, sift together the flour, cocoa powder, and baking soda. Set aside.
In a large bowl, beat the butter on medium speed with an electric mixer until smooth and creamy.
Add sugar, brown sugar, salt, and vanilla and beat for 2 more minutes. Add half of the flour mixture and mix on low until just combined. Add remaining flour and mix until combined. Stir in chocolate chips.
Turn dough out onto a countertop or work surface and divide dough in half. Shape each section into logs that are 1 1/2 inches in diameter. Wrap each log in plastic and chill until firm, at least 3 hours.
Once chilled, slice logs into 1/2-inch thick rounds.
Place rounds on prepared baking sheets 1-inch apart. Bake until firm around the edges but soft in the center, about 12 minutes.
Let cool 5 minutes on baking sheet before transferring to a wire rack to cool completely.
