Combine the 3 tablespoons white sugar and the cinnamon in a small bowl and set aside.
Blend dark brown sugar and white sugar in a large bowl with mixer on medium speed. Add butter and blend until grainy. Add eggs and vanilla extract, mixing until light and fluffy.
Whisk flour, baking soda and salt together in a separate bowl. Add to sugar mixture, mixing at low speed just long enough to combine. Overmixing makes tough cookies!
Roll dough into 1inch balls, then roll each ball into cinnamon-sugar to coat. Place cookies on ungreased cookie sheets and bake at 300° for 18 to 20 minutes. Remove from sheets and let cool on racks.
