Preheat your oven to 350 degrees
In a large bowl, mash 2 medium overly ripe bananas until smooth and add 1/2 cup of vegetable or canola oil, 1 cup of light brown sugar, 2 egg yolks and 2 teaspoons of vanilla extract. Mix until fully combined
In a separate bowl, combine 3/4 teaspoon of baking soda, 1/2 teaspoon of salt, 1 1/2 teaspoon of ground cinnamon, 1/4 teaspoon of nutmeg, 1/4 teaspoon of all spice, a pinch of ground ginger and 2 1/4 cups of all purpose flour and then add this in with the banana and egg yolk mixture
Mix until the dry ingredients are just incorporated and then add 3/4 cup of milk chocolate chips and 2/3 cup of finely chopped walnuts
Using a greased cookie dough scoop, scoop heaping tablespoons of dough onto parchment lined baking sheets leaving at least 2 inches of space between each portion of dough
Bake the cookies in a 350 degree oven for 10-11 minutes or until the cookies are lightly golden
As soon as you transfer the cookies out of the oven, bang the baking sheet onto your counter top a few times to deflate the freshly baked cookies (optional)
Garnish the warm cookies with finely chopped chocolate and walnuts (optional)
Store room temperature leftovers in an airtight container