Remove the frozen banana half from the freezer and cut it into large pieces so the blender can more easily process the ingredients. Roughly chop the roasted mixed nuts and set them aside on the work surface along with the flax seeds and fresh mint.
Place the frozen banana pieces along with the Greek yogurt, scoop of vanilla protein powder and almond milk into the blender. Turn on the blender and mix everything thoroughly until a completely smooth and thick mixture forms without any lumps.
Pour the thick yogurt mixture directly from the blender into a large bowl. Use a spatula to scrape the sides of the blender clean. Then sprinkle the roughly chopped roasted nuts and the tablespoon of flax seeds evenly over the top of the mixture.
Place a few leaves of fresh mint in the center of the bowl as a final garnish. Serve the smoothie bowl immediately so the texture stays cold and firm while eating.