1. Preheat oven to 350 degrees Fahrenheit. Mix together flour, soda and salt in a small-medium bowl and set aside. Lightly grease a cookie sheet.
2. In a large bowl, mix together oil, sugar, milk, and vanilla. Mix in mashed banana and baking powder. Add ingredients in the small bowl and stir well.
3. Once it is well stirred, lightly mix in the crushed walnuts. Drop by tablespoons onto prepared cookie sheet. Bake 9-12 minutes (depending on your oven).
For a less greasy mixture, I'm sure you could add more milk and less oil, but I haven't tried it yet. And this recipe only makes 12-13 cookies for me, but I like to make giant cookies (heaping tablespoons for me!).'