1-Mix the wet ingredients: In a large bowl, whisk together vegetable oil, granulated sugar, eggs, and vanilla until smooth and slightly thickened, about 1 minute.

2-Add the dry ingredients: Sift together cocoa powder, flour, cornstarch, baking powder, salt, and espresso powder (if using); gradually stir into the wet mixture just until combined—do not overmix.

3-Chill the dough: Cover and refrigerate the dough for at least 2 hours (overnight is better) to make it less sticky and easier to shape.

4-Preheat and prep: Preheat oven to 350°F (180°C) and line two baking sheets with parchment paper.

5-Scoop and roll: Portion dough into 1.5 tablespoon balls; roll each first in granulated sugar, then coat generously in powdered sugar (thick layer creates the cracks).

6-Bake: Place coated balls on sheets 2 inches apart and bake for 10–12 minutes, until slightly underbaked and soft in the center.

7-Cool: Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.