In large bowl, stir pancake mix, milk, eggs, oil and mashed bananas.
Spread 1/4 cup pancake batter on skillet. When pancake begins to bubble, use spatula to flip. Cook until golden brown on each side. Repeat with remaining batter.
To make whipped cream: In small bowl, whip heavy cream and sugar until thickened.
Top pancakes with homemade whipped cream, banana slices, walnuts and syrup.