In a large bowl sift together the flour, baking powder and salt. Whisk together and set aside.
Add the oil and granulated sugar to the bowl of a stand mixer fitted with a paddle attachment and beat together. Scrape bowl down and mix until combined.
Add the cocoa powder in and mix on low scraping the bowl down halfway through. If you're using the espresso powder you can add in at this point.
Add the eggs and vanilla in then mix until well combined.
Dump the flour mixture in and mix on low. Scrape bowl down and mix until combined.
Cover in plastic and refrigerate overnight or for at least 4 hours
Preheat oven to 350F. Use a small ice cream scoop or tablespoon to scoop out the chilled dough and roll into roughly one inch balls with your clean palms.
Roll dough in powdered sugar and place on parchment lined baking sheet about 2 inches apart.
Bake for 10-12 minutes at 350F. The cookies' edges will be set but the center will finish baking out of the oven.
Measure your flour correctly! Adding too much flour to the recipe is the most common mistake. The best, and easiest way to measure flour is by using a scale. If you don't have one then fluff your flour with a spoon, sprinkle it into your measuring cup, and use a knife to level it off.
Try to make the dough a day ahead, it really needs time to set up and will be so much easier to roll.
I actually love making these cookies with olive oil instead of vegetable oil; give it a try!
If you're not into cookies covered in powdered sugar try rolling them in sanding sugar. They'll still have some visual interest and there's no chance of inhaling sugar when you bit into them.