Preheat your oven to 400 degrees F. Prepare a 12-cup muffin pan by lining it with muffin liners and spraying the inside with nonstick cooking spray. This step is crucial as it prevents the muffins from sticking to the liners.
In a large bowl or blender, combine the Greek yogurt, almond milk, mashed bananas, oil, egg, and vanilla. Blend or mix until you have a smooth and well-combined mixture. It should be creamy and uniform.
Transfer this mixture to a large bowl and add in the Coach’s Oats. Stir gently until combined, then let it sit for around 5 minutes. This allows the oats to soften, making for a denser muffin.
After 5 minutes, gently fold in the whole wheat pastry flour, flaxseed meal, cinnamon, baking soda, and salt. Mix until just combined; be careful not to overmix as this can lead to tough muffins.
Finally, fold in the dark chocolate chips and the chopped nuts. Ensure they are evenly distributed throughout the batter.
Scoop the batter into the prepared muffin liners, filling each about two-thirds full to allow for rising during baking.
Bake in the preheated oven for 7 minutes at 400 degrees, then reduce the temperature to 350 degrees without opening the oven door! Continue baking for an additional 13 to 16 minutes.
Check for doneness by inserting a toothpick into the center of a muffin; it should come out clean or with just a few crumbs attached.
Once baked, allow the muffins to cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.
Enjoy your Chocolate Chip Banana Oatmeal Muffins warm or at room temperature, savoring every delicious bite!