In a skillet, melt butter over medium heat.
Add brown sugar and sliced bananas, and stir continuously coating bananas. As soon as sauce thickens, immediately remove from heat and set aside.
In a large bowl, whisk flour, granulated sugar, baking powder, baking soda and salt.
Stir in milk, melted butter, eggs, mashed bananas until just moistened.
Fold in walnuts.
Warm a skillet over medium heat and brush with vegetable oil. Ladle mix, 1/4 cup at a time into skillet. When tops are bubbling and edges appear dry, flip until cook until golden. Repeat until all batter is gone. Keep pancakes in warm oven until ready to serve.
Serve warm pancakes with caramelized banana topping drizzled on top, add a few walnut pieces on top.