1. In a medium bowl, whisk together the flour, cocoa powder, baking powder, salt, and instant espresso powder until well combined and no cocoa lumps remain.

2. In a large mixing bowl, whisk the granulated sugar, brown sugar, and vegetable oil until thick and glossy.

3. Add the eggs one at a time, whisking well after each, then whisk in the vanilla extract until the mixture is smooth.

4. Add the dry ingredients to the wet ingredients in two additions, stirring gently with a spatula just until no dry flour remains.

5. Fold in the chocolate chips or chunks until evenly distributed; the dough will be thick and sticky.

6. Cover the bowl and refrigerate the dough for at least 2 hours, or up to overnight, until firm enough to scoop and roll.

7. When ready to bake, preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.

8. Place the powdered sugar in a shallow bowl. Scoop tablespoon-sized portions of chilled dough and roll quickly into balls with your hands.

9. Roll each dough ball generously in powdered sugar, coating it on all sides, then place on the prepared baking sheets about 2 inches apart.

10. Bake for 10–12 minutes, or until the cookies are puffed, deeply crackled on top, and just set around the edges while still soft in the center.

11. Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely and allow the centers to set and stay fudgy.

12. Once fully cooled, store the cookies in an airtight container at room temperature for up to 4–5 days, or freeze for longer storage if desired.