Preheat the oven to 375.
In a large bowl mash the bananas until smooth.
Mix the peanut butter into the bananas and then mix in the maple syrup, cinnamon, vanilla, flax, chia, milk and salt. Mix well.
Add in the oats and nuts if using. Mix until everything is incorporated.
Fill lined muffins cups about 3/4 full. This recipe makes 10 muffins.
Bake at 375 about 25 minutes.