Sift flour, cocoa powder, baking powder, instant coffee, and salt into a medium bowl using a strainer. Whisk them together.
Combine eggs, oil, granulated sugar, and vanilla in a large bowl. Whisk them together until well combined.
Add the dry ingredients (flour mixture) to the wet ingredients. Mix with a spatula until just combined and no more flour is visible.
Cover with plastic wrap and refrigerate it for 2 to 4 hours. You can also freeze it for 30 minutes to an hour.
Make 12 to 14 cookie dough balls using a #40 cookie scoop or about 1½ tablespoons (30 to 35 grams).
Coat them generously with powdered sugar and arrange them on a parchment paper-lined baking sheet about 2 inches apart.
Bake in a 350° F (177° C) preheated oven for 9 to 10 minutes, depending on your oven. They are ready when the tops have cracked and the center looks slightly glossy.
Allow the cookies to cool before serving.
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Notes
Unsweetened cocoa powder: Use Dutch-process cocoa powder for darker, fudgier cookies. Hershey's "Special Dark" Cocoa Powder is an example.
Instant coffee: You won't taste the coffee in the cookies but a more intense chocolate flavor. Half as much espresso powder can be used.
Oil: Use a neutral or mild-tasting oil like canola, avocado, or other vegetable oils.