Preheat oven to 325℉, line a cookie sheet with parchment and set aside.
In a medium/large mixing bowl, combine butter and slowly mix in powdered sugar 3-4 tablespoons at a time*. Once all powdered sugar is added, beat well by hand to whip it up. Sift in cocoa powder and add salt. Mix until completely incorporated.
Scoop in the yogurt, and vanilla extract, mixing well again until fully incorporated. The dough is SO delicious at this point, try not to eat it all. Stir in the flour, then fold in the chocolate chips.
Using your '1 tablespoon' spoon, measure out 1 tablespoon of dough and roll into a ball. Place on parchment about 1-2 inches apart and repeat the process. If dough does not hold its shape, try adding 1-2 tablespoons more flour, or place in fridge to firm up.
After rolling out all balls, bake for 10 minutes until just set. Leave the cookies to cool/finish baking on the pan for 5-10 minutes. Remove to wire rack to finish cooling to room temperature. Once they are cool enough, roll to coat in powdered sugar.