Add 1 (12 ounce) bag of chocolate chips to a large, microwaveable bowl. Top with butter and microwave at half power for 2 minutes.
Stir until smooth. If needed, continue to microwave in 30 second bursts at half power until the mixture can be stirred to a smooth consistency. Set aside.
In a small bowl. whisk together eggs, sugar, and vanilla. Set aside.
In another small bowl, combine cocoa, flour, baking powder, espresso powder, and salt until fully mixed and no lumps remain.
Stir egg mixture into chocolate, just until combined. Fold flour mixture into chocolate mixture until just combined. Stir in second bag of chocolate chips.
Drop by two tablespoons sized dollops onto a baking sheet prepared with parchment paper. Bake for 10-12 minutes at 325°F until done.
Cool on the baking sheet for 5 minutes, before removing cookies and placing them on a separate flat surface to cool completely.