Sift together flour, baking powder, salt, and cocoa in medium bowl.
Melt chocolate in a medium bowl set over pan of almost-simmering water. Stir until smooth. Alternatively, you can melt the chocolate in the microwave. Heat on medium high for about 1 minute to start with. Remove from the microwave and stir. Repeat heating at shorter intervals, 15 to 20 seconds, stirring in between, until the chocolate is completely melted.
Beat eggs and vanilla with fork. Sprinkle coffee powder over to dissolve.
In the bowl of a standing mixer, beat butter at medium speed until smooth and creamy.
Beat in sugars until combined.
Reduce speed to low and gradually beat in egg mixture until incorporated.
Add melted chocolate and beat until combined, scraping down bottom and sides of bowl with rubber spatula.
Add flour mixture and mix until combined. Do not overbeat.
Stir in chocolate chips or chunks.
Cover with plastic wrap and let stand at room temperature until consistency is scoopable and fudgelike, about 30 minutes. If your kitchen is too warm, place in the refrigerator. The dough should be 75 degrees F before baking.
Heat oven to 350 degrees F and set oven racks to the top and bottom thirds.
Line 2 rimless cookie sheets with parchment paper.
Scoop dough onto parchment-lined cookie sheets with 1¾-inch diameter ice cream scoop.
Bake cookies until edges have just begun to set but centers are still very soft, about 10 minutes, switching cookie sheets from top to bottom racks halfway through baking.
Cool cookies on sheets about 10 minutes. Slide parchment with cookies onto wire rack and cool to room temperature.