Somewhere between a brownie and a cookie, these fudgy balls, with their dramatically crinkly exteriors, are rolled in powdered sugar. They're a festive treat you'll want to keep making long after the holidays are over. (This recipe yields 24 cookies.)
In a double boiler or heatproof bowl set over (but not touching) barely simmering water in a pot, temper (melt) the chocolate, stirring occasionally with a rubber spatula. Keep warm.
Measure your dry ingredients with the "dip and sweep" method: Dip a measuring cup or spoon into the dry ingredient, then use the back of a knife to sweep away the excess and level the surface. Whisk together flour, cocoa, baking powder, and salts in a bowl, and set aside.
Crack the eggs into a bowl and add the vanilla.In the bowl of a stand mixer fitted with a paddle attachment, mix the oil and sugar on low speed, 1 minute. Turn mixer off, add melted chocolate, and mix to combine on low speed, 30 seconds. Turn mixer to medium and add the eggs and vanilla, one egg at a time, mixing briefly to incorporate before adding the next. Turn mixer off and scrape down the sides of the bowl. Mix again on medium speed, 30 seconds.
With the mixer off, add the dry ingredients all at once. Mix on low speed until the dough comes together but still looks shaggy, 30 seconds. Do not overmix. Remove bowl from mixer and use a rubber spatula to bring dough together by hand. Wrap dough in plastic wrap and refrigerate 1 hour.
Bake: Preheat oven to 325 F. Line two rimmed baking sheets with parchment paper. Put the confectioners' sugar in a bowl. Portion the dough into 24 mounds, then roll into balls. Coat the balls completely in the sugar; when you're through, they should resemble snowballs. Evenly space the balls on the prepared baking sheets, 12 to a pan. Bake 8 minutes, then rotate the pans and bake another 4 minutes.
After 12 minutes, remove from the oven and let settle on the pan for 2 minutes. The cookies will have a crinkly appearance but might still look under cooked in the middle. This is fine, because they'll continue cooking out of the oven while they’re settling. Remove to a wire rack to cool completely. Devour.