In a medium bowl, whisk together Dutch-process cocoa powder, granulated sugar, and vegetable oil until shiny and smooth.

Whisk in eggs one at a time, followed by pure vanilla extract, beating until glossy and well combined.

In a separate bowl, stir flour, baking powder, and salt. Fold into the chocolate mixture with a spatula just until a soft, shiny dough forms. Cover bowl tightly and chill in the refrigerator for at least 2 to 4 hours (or overnight) until firm.

Preheat oven to 350°F (175°C) and line two large baking sheets with parchment paper. Place granulated sugar in one small bowl and powdered sugar in a second bowl.

Scoop 1-tablespoon portions of chilled dough and roll between your palms into smooth round balls.

Roll each dough ball first in granulated sugar (this prevents powdered sugar from melting), then coat very heavily in powdered sugar so no chocolate dough shows through.

Place balls 2 inches apart on prepared sheets. Bake at 350°F for 10 to 12 minutes until cookies have puffed and crinkled across the top with soft fudgy centers. Let cool on the baking sheet for 5 minutes, then transfer to a wire rack.