Pre-heat the oven to 425 degrees, and line a muffin tin with unbleached paper cup liners. Mash 4 bananas in the bottom of a medium mixing bowl until smooth. There can be a few small pieces throughout.
Add the avocado oil, coconut milk, eggs, and vanilla and whisk with the fork to combine with the mashed bananas.
Blend the pecans and the walnuts into a fine meal, and add them to the wet ingredients in the bowl. Add the rest of the ingredients to the bowl, and use a rubber scraper to stir the batter until it is just combined.
Scoop the batter into your lined muffin tin, filling the muffins cups all the way to the top if you want the larger, bakery style muffins. You will get 12 large, bakery style muffins perfectly, or you can make them smaller and get 18 regular sized muffins.
Put the muffins in the oven, and bring the temperature down to 400 degrees. Bake at 400 degrees for 25-30 minutes. Check your muffins around the 25 minute mark in case our ovens run differently. The muffins should spring back to touch, and be golden brown on the top.