Preheat the oven to 350°F. Grease a 9×5" loaf pan with nonstick cooking spray and line with parchment paper. 

In a large mixing bowl, mash ripe bananas until mostly smooth (a few clumps are ok). Whisk in melted butter, maple syrup, almond butter, brown sugar, egg, and vanilla until creamy.

Add flours, cinnamon, nutmeg, baking powder and soda, and salt. Use a wooden spoon or spatula to combine until a smooth and pourable batter forms. Fold in walnuts, shredded carrot, and chocolate chips. Pour into prepared loaf tin. (Optional): sprinkle over additional chocolate chips and walnuts. 

Bake for 50-55 minutes until top is golden brown and toothpick inserted comes with a few moist crumbs. If top browns too quickly, you can cover top loosely with foil.

Remove from oven and cool in the loaf pan for 10 minutes before transferring to a wire cooling rack. Cool for at least 1-2 hrs before slicing and serving. 

Before serving, make icing by whisk together all ingredients until creamy. 

Cover or tightly wrap in plastic wrap and store at room temperature for up to 5 days or in the refrigerator for up to 1 week.