Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or lightly grease each cup with cooking spray.
In a large mixing bowl, whisk together the egg, Greek yogurt, milk, and pure maple syrup until smooth and well combined.
Stir in the rolled oats and vanilla protein powder until everything is fully combined. Let the mixture sit for about 10 minutes to allow the oats to soften slightly and absorb the liquid.
Gently fold in the mini chocolate chips until evenly distributed throughout the batter.
Divide the batter evenly among the prepared muffin cups, filling each about 3/4 full.
If using, place a few blueberries on top of each muffin for a fresh and colorful touch.
Bake for 20–25 minutes, or until the muffins are set and a toothpick inserted in the center comes out clean.
Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack to cool completely. Enjoy warm or store in an airtight container for up to 3 days.