Start by cracking the eggs into a large mixing bowl, then add the Greek yogurt, mashed banana, and vanilla extract. Using a whisk, mix everything together until the mixture becomes completely smooth and creamy. Make sure the banana is fully mashed with no large lumps, as this helps create a soft and even texture in the final muffins.

Add the rolled oats, protein powder, baking powder, and cinnamon into the bowl. Stir gently using a spatula or spoon until all the dry ingredients are evenly incorporated into the wet mixture. Take your time to mix just until combined—avoid overmixing, as this can make the muffins dense instead of soft and fluffy.

Slowly pour in the milk a little at a time while stirring continuously. This helps you control the consistency of the batter. Keep mixing until you reach a thick but pourable texture—similar to a thick pancake batter. If it feels too thick, add a small splash of milk; if too thin, let it sit for a minute so the oats can absorb some moisture.

Prepare your muffin tray by lining it with paper liners or lightly greasing each cup. Using a spoon or scoop, divide the batter evenly into each muffin cup, filling them about three-quarters full. This allows enough space for the muffins to rise without overflowing.

Place the tray into a preheated oven at 180°C and bake for 18–22 minutes. Keep an eye on them toward the end—when the tops look set, slightly golden, and spring back lightly when touched, they are ready. You can also insert a toothpick into the center; if it comes out clean, the muffins are fully baked.

Remove the muffins from the oven and let them cool in the tray for a few minutes before transferring them to a plate or rack. Allow them to cool slightly before serving so they firm up properly and develop the best texture, making them easier to handle and more enjoyable to eat.