In a bowl, beat the butter with an electric mixer until fluffy. Add the brown sugar and granulated sugar and beat until well blended. Beat in the egg and vanilla until thickened. Beat in 2/3 cup of the flour along with the baking soda and salt. Stir in the remaining 1 cup flour; the dough will be soft.
Divide the dough in half. Wrap each half in wax or parchment paper or plastic wrap and shape it into a 6-inch log. Refrigerate until firm.
Preheat the oven to 350°. Using a thin knife, slice each log 1/8 to 1/4 inch thick. Arrange the cookies 1 inch apart on buttered cookie sheets and bake for 10 to 15 minutes, or until lightly golden.
For these creative cookies, add the extras to the dough with the final portion of flour. Roll the logs in the flavorings before chilling.
Add 1/2 cup finely chopped crystallized ginger. Roll each log in 1/3 cup finely chopped blanched almonds.
Add 3 tablespoons poppyseeds and 1 tablespoon grated lemon zest. Roll each log in 1 tablespoon poppyseeds.
Add 1 teaspoon freshly ground nutmeg, 1 teaspoon cinnamon and 1/4 teaspoon ground cloves. If desired, roll each log in 1/3 cup finely chopped walnuts.
Roll each log in 1 1/2 tablespoons very finely ground French-roast coffee.
Add 1 cup finely chopped toasted pecans. Roll each log in 1/3 cup finely chopped toasted pecans.
The logs can be stored in a plastic bag and refrigerated for up to 1 week or frozen for up to 2 months.