In a medium bowl, whisk together the flour, cocoa, salt, coffee/espresso powder, and baking power.
In a separate large bowl, preferably with an electric mixer, combine the vegetable oil and granulated sugar. Beat for 2 minutes. Add eggs and vanilla; mix until combined. Add in flour mixture, and mix until combined.
Cover the mixture with plastic wrap (either in the bowl, or just dump it out onto the counter and form a disc). Refrigerate for 2 hours or overnight.
Preheat the oven to 350ºF. Line a cookie sheet with parchment paper. Place the powdered sugar into a small bowl. Roll the dough into 1-inch balls, then roll in the powdered sugar to coat.
Place on the prepared cookie sheet, spaced 2 inches apart. Bake for 10 minutes. When they come out they’ll be soft in the middle and slightly crisp on the outside.