Ingredients:
2 1⁄2 cups semisweet chocolate chips, divided
8 Tbsp. (1 stick) unsalted butter
1 cup all-purpose flour
2 Tbsp. Dutch-process cocoa powder
1 tsp. baking powder
1⁄2 tsp. kosher salt
3 large eggs
1 cup granulated sugar
1⁄3 cup packed light brown sugar
2 tsp. pure vanilla extract
Directions:
In a medium microwave-safe bowl, combine 2 cups of the chocolate chips and the butter. Microwave on high in 20-second intervals, stirring thoroughly between intervals, until completely melted and smooth. Scrape mixture into the bowl of a stand mixer fitted with the paddle attachment; let sit for 20 minutes to cool.
While the chocolate mixture is cooling, sift together the flour, cocoa, baking powder and salt in a separate medium bowl. Preheat oven to 375°. Line 2 large baking sheets with parchment paper.
Add eggs, granulated sugar, brown sugar and vanilla to the cooled chocolate mixture; beat on medium speed until thoroughly combined. Reduce speed to low. Slowly pour the flour mixture into the chocolate mixture, and mix until thoroughly combined. Add the remaining 1⁄2 cup chocolate chips, and mix briefly to incorporate fully.
Using a 1-ounce scoop, portion dough onto one prepared baking sheet. You do not need to space them out. Chill until firm, about 45 minutes.
Working in batches, place the chilled cookies 2 inches apart on the other prepared room-temperature baking sheet.
Bake until the edges are set, 12 to 14 minutes. The centers of the cookies will appear and feel soft when hot but will set as they cool. Let cool on baking sheet 5 minutes, then transfer to a wire rack to cool completely. Repeat with the remaining cookie balls. Store in an airtight container for up to 5 days.