Preheat oven to 180°C/360°F, and line a 8x4 inch loaf pan with parchment paper.
In a large bowl, mash the bananas with a fork, then mix in all the remaining wet ingredients.
In a another bowl mix together the dry ingredients.
Gently fold the dry ingredients into the wet ones. Mix until fully combined, being careful not to overwork the mixture.
Finally add chopped carrots and nuts. Pour the mixture into the prepared loaf pan and bake for about 40-45 minutes, or until a toothpick inserted into the center comes out clean.
In the meantime, whisk the ricotta cheese with sugar, until you get a smooth and rich cream. Add freshly grated orange zest and mix until just combined. Refrigerate until ready to use.
When the banana bread is ready, remove the pan from the oven and allow to cool. Then remove the bread from the pan and arrange on a cooling rack.
Spread the ricotta frosting on top, sprinkle with chopped walnuts and grated carrot, and serve.