On a separate mixing bowl, mix oil, sugar and vanilla for 1 minute. Add eggs, one by one, mixing after each addition. Gradually add dry ingredients, mixing until just combined*. Fold in carrots and walnuts
Using a piping bag, fill donut tins 2/3 full*. Bake for 10-11 minutes or until a toothpick inserted in the middle comes out clean. After 1 minute remove from tin and place on a cooling rack to cool completely*
Beat cream cheese for 1 minute on medium speed, add powdered sugar and vanilla and beat until just combined. Frost donuts and top with chopped walnuts
* Do not overbeat* Don't fill them more than 2/3 to avoid them from overflowing* I like to flip the donut tin completely one minute after they're out of the oven