Preheat oven to 375 degrees. Spray 9" x 9" pan with nonstick baking spray.
Spread the banana slices on the bottom of the dish and top with ¾ cup craisins, ¼ tsp of cinnamon and ½ Tbsp of the sweetener of choice.
Cover with foil and bake until the bananas are soft, about 15 minutes.
While that is baking, mix together the oats,⅛ cup of the nuts, baking powder, remaining cinnamon (¾ tsp), salt, brown sugar, and remaining sweetener (1½ Tbsp) in a large bowl. In another bowl whisk the milk, egg and vanilla extract.
Once the bananas are soft, remove the foil and pour the oat mixture over top.
Pour the milk mixture over top of the oats, making sure to evenly distribute it.
Top with remaining craisins (¾ cup) and walnuts (⅛ cup) and bake for 30 minutes or until golden brown.