The level of ripeness is a point of contention between many home cooks, but it is essential to remember that your bananas need to be at least fully ripe to be sweet. The mushier and the riper they are, the richer and sweeter the banana flavor will be.
Preheat oven to 350 degrees. Grease and flour a 4 by 8-inch loaf pan.
In a large bowl, mix together the mashed bananas and melted butter. Mix in the sugar, egg, vanilla, and bourbon. In a separate bowl, whisk together flour, baking soda, spices, and salt. Gradually incorporate dry ingredients into the banana mixture. Gently, fold in the in chopped nuts.
Pour mixture into loaf pan using a spatula. Bake for 50 minutes to 1 hour, or until a toothpick inserted into the center of the loaf comes out clean.