01 - Preheat oven to 350°F (175°C). Prepare a 12-cup muffin tin by lining it with paper liners or lightly greasing the cups.
02 - In a large mixing bowl, combine the rolled oats, whole wheat flour, unsweetened cocoa powder, chocolate protein powder, baking powder, baking soda, and salt.
03 - In a separate bowl, whisk together the eggs, Greek yogurt, unsweetened applesauce, milk, honey or maple syrup, melted oil, and vanilla extract until thoroughly blended and smooth.
04 - Pour the wet ingredients into the bowl with the dry ingredients. Mix until just combined, ensuring not to overmix the batter.
05 - Gently fold the dark chocolate chips into the batter.
06 - Divide the prepared batter evenly among the 12 muffin cups. If desired, sprinkle additional dark chocolate chips on top of each muffin.
07 - Bake for 18 to 22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
08 - Allow the muffins to cool in the muffin tin for 5 minutes before carefully transferring them to a wire rack to cool completely.