Preheat oven to 200 degrees C. Line a baking tray with baking paper.
In a medium size mixing bowl, sift together flour, bicarb soda and salt. In a separate small bowl, combine 2 tablespoons brown sugar with cinnamon, set aside.
In a medium size mixing bowl, beat together the rest of the brown sugar with the butter or margarine, vanilla and banana essence until the mixture is light in texture. Beat in the eggs. Mix in the banana. Slowly mix the flour mixture into the egg, banana and sugar mixture. Fold in walnuts. Drop the dough by teaspoonful onto the prepared baking tray. Sprinkle the biscuits with the mixture of brown sugar and cinnamon prepared earlier.