Mix dry ingredients: In a medium bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt. Set aside.
Combine wet ingredients: In a large bowl, whisk granulated sugar, vegetable oil, eggs, and vanilla extract until smooth. Stir in melted chocolate chips.
Form dough: Gradually add dry ingredients to wet, stirring until just combined. The dough will be soft and sticky.
Chill dough: Cover and refrigerate for at least 2 hours (or up to 24 hours).
Preheat oven: Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper. Place powdered sugar in a shallow bowl.
Shape cookies: Scoop tablespoon-sized dough portions and roll into balls. Roll each ball generously in powdered sugar to coat.
Bake: Place dough balls 2 inches apart on baking sheets. Bake for 10-12 minutes, until edges are set but centers are soft.
Cool: Let cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack.
