All cookies are best hot from the oven, so I mix up this entire batch, divide it into eight, 1-cup sections, make each section into a long roll about 1-inch in diameter, and freeze each roll in separate zipper bags. When I am expecting guests or I feel like baking cookies, I thaw out a roll or two, add in the extras, and bake. To bake them without extras, I cut the frozen roll into 3/4-inch segments, place on the cookie sheet, and bake. If the dough is frozen, add one minute to the baking time.
Cream together:
2 cups butter
2 cups sugar
1 cup light brown sugar, firmly packed
4 eggs
1 tablespoon cream of tartar
2 teaspoons baking powder
1 tablespoon vanilla
1 teaspoon salt
Add to creamed mixture:
6 1/2 cups all-purpose flour
1/4 cup milk or half and half
Mix thoroughly and divide dough into eight, 1-cup parts. This dough will keep for several days in the refrigerator. For longer storage, freeze in zipper bags. Each roll will make approximately 2 dozen cookies. Bake on greased cookie sheets at 350 degrees for 12 minutes.
The following additions are to be added to a 1-cup part. Bake as above:

Chocolaty Chocolate Chip: Knead in 1 tablespoon cocoa powder and 2/3 cup of semisweet chocolate pieces (or peanut butter pieces). Shape into balls and bake.

Coconut/Almond: Knead in 1 cup flaked coconut (I use fresh coconut.) and 1/2 teaspoon almond extract. Roll into balls and press half of a maraschino cherry on top. Make coffee. Invite me over. My all-time favorite! Yum!

Pecan: Knead in 1/2 cup finely chopped pecans.

Ginger: Stir in 1 tablespoon molasses and 1/4-1/2 teaspoon ground ginger. Shape into balls and roll in granulated sugar.

Snickerdoodles: Shape into balls and roll in a mixture of 2 parts granulated sugar to 1 part cinnamon.

Fruit and Spice: Add 1/2 cup chopped dried fruit (raisins, dates, apricots, etc. — clean out your cupboards!), 2 tablespoons brown sugar, 1/2 teaspoon ground cinnamon, and 1/4 teaspoon cloves. Drop by heaping teaspoons full 2 inches apart on cookie sheet.

Orange or Lemon: Stir in 1/4 teaspoon grated orange or lemon peel, 1/4 cup sugar, and 4 teaspoons frozen orange or lemonade juice concentrate (thawed). Drop by heaping teaspoonfuls 2 inches apart on cookie sheet. When the cookies are still hot, brush the tops with either thawed lemonade concentrate or orange juice. Sprinkle with sugar.

Oatmeal: Knead in 1 cup of oatmeal, 1/2 teaspoon cinnamon, and 1/2 cup of raisins or dates. Shape into balls, flatten slightly with a buttered spatula.