Preheat oven to 350F(175C)
- Beat butter, sugar and vanilla until creamy.
- Add oil and water.
- Keep mixing on lowest speed.
- In a separate bowl whisk flour and baking powder.
- Gradually add to the butter mixture while mixing on a low speed.
- Add ground walnuts and mix just until ingredients are incorporated.
- Place the tins on cookie sheets and bake 22-25 minutes.
- While still warm turn the tins upside down as it will be easier to remove the cookies from the tins.
- Once the cookies cool down, squeeze a tin just a little and the cookie should come out easily.
- Roll cookies in powdered sugar.