Grease and line a slow cooker with parchment paper.

In a large bowl, cream together the softened butter and sugar until light and fluffy.

Beat in the eggs one at a time, then stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients1 to the wet ingredients, alternating2 with the milk, until just combined.

Stir in the mashed bananas.

If desired, fold in the chopped walnuts or chocolate chips.

Pour the batter into the prepared slow cooker.

Cover and cook on low for 2-3 hours, or until a toothpick inserted into the center comes out clean.

Remove the bread from the slow cooker and let it cool before slicing.