1 cup semisweet chocolate chips (or dark chocolate chunks or chopped bars (180g))
Instructions:
Preheat oven to 375F. Line two baking sheets with parchment paper.
In a bowl, sift together flour, cocoa powder, baking soda, and salt.
In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugars on medium speed until very light and fluffy, about 3 minutes.
Add egg and vanilla and beat until well combined, scraping down the sides of the bowl as needed.
With the mixer on low speed, gradually add the flour mixture, mixing just until combined. Stir in the chocolate chips.
Scoop 1½ tablespoon-sized balls of dough on the cookie sheet, place about 2 inches apart.
Bake for 10 minutes or until cookie edges are firm and the center appears dry. Let cool on the sheets for 5 minutes. Transfer to wire racks to continue cooling. Store baked cookies in an airtight container for up to 5 days.