Preheat oven to 350 degrees F. and line a cookie sheet with parchment paper.
In a large bowl, combine all dry ingredients.
In a medium bowl, whisk eggs. Add to dry ingredients and stir until combined.
Stir in vanilla and greek yogurt.
Melt coconut oil in the microwave or preheated oven. Add to dough and stir until combined.
Fold in walnuts and dark chocolate.
Cover bowl and chill in the refrigerator for 8 minutes.
Form 16 even (roughly 1-inch) balls of dough and place half of them on the lined baking sheet. Press down on each ball of dough into cookie shape. (They won't spread out very much.)
Bake for 12-15 minutes, or until lightly browned and hardened. Let cool completely and save in airtight containers in room temperature.