In a large bowl, whisk together the flour, cocoa powder, baking powder, baking soda, salt, and sugar until well combined. Set aside.
2 cups all-purpose flour, ½ cup cocoa powder, 2½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt, 1 cup granulated sugar
In a separate bowl, whisk the greek yogurt, oil, eggs, buttermilk, and vanilla until well combined.
¼ cup plain greek yogurt, ⅔ cup vegetable oil, 2 large eggs, 1 cup buttermilk, 2 teaspoon vanilla extract
Pour the wet ingredients into the dry and use a rubber spatula to mix until just combined. Gently fold in the oreo crumbs and chocolate chips. Be careful not to overmix, the batter should be thick.
½ cup mini chocolate chips, ½ cup chopped oreos
Cover the bowl and allow the muffins to rise for 1 hour.
Preheat the oven to 425℉. Line a muffin tin with liners or spray with nonstick spray and set aside.
Pour the batter evenly into the prepared muffin pan, filling each one almost to the top (using about ¼ cup of batter)
Bake the muffins at 425℉ for 8 minutes, and then reduce the oven temperature to 350℉. Continue baking for another 7-10 minutes until a toothpick inserted in the middle of a muffin comes out clean.
Allow the muffins to cool in the pan for about 5 minutes before removing them. Place them on a wire cooling rack to cool completely.