I baked it according to this recipe:

http://www.food.com/recipe/starbucks-banana-walnut-bread-384181

But I changed a bit.
Ingredients:

2 cups flour

1 tsp baking soda

1/4 tsp salt

1 egg

1 cup sugar

1/2 cup olive oil ( original recipe said vegetable oil)

1/2 tsp vanilla

3 mashed banana

1/2 cup walnut

1/3 cup walnut

1. Preheat oven to  170 degree C.

2. Mix flour, baking soda and salt in a bowl.

3. Blend egg, sugar and olive oil in another bowl.

4. Combine flour mixture with egg mixture. Blend well.

5. Add in vanilla and mashed banana.

6. Fold in 1/2 cup walnut. ( I just put walnut in a plastic bag and roll it with a rolling pin).

7. Place batter in baking pan.

8. Sprinkle 1/3 cup walnut on the top.

9. Bake for around 50 mins, till toothpick comes out clean.

It tastes really great.