THE MOTHER OF ALL BUTTER COOKIES (WITH ENDLESS VARIATIONS)

Steps:

• Preheat oven to 375 degrees. Combine flour, cornstarch, sugar and salt in a food processor, and pulse once or twice. Add butter, and pulse 10 or 20 times, until butter and flour are well combined. Add vanilla and egg and pulse 3 or 4 times. Add about half the milk and pulse 2 or 3 times. Add the remaining milk a little at a time, pulsing once or twice after each addition, until the dough holds together in a sticky mass.
• Remove the dough from the machine to one or more bowls. Make cookies as described in Step 3, or make any of the variations below.
• To make cookies, drop rounded teaspoons of dough (you can make the cookies larger or smaller, if you like) onto a nonstick baking sheet, a sheet lined with parchment paper or a lightly buttered sheet. If you want flat cookies, press the balls down a bit with your fingers or the back of a spatula or wooden spoon. Bake 11 minutes, or until the cookies are done as you like them. Cool on a rack, then store, if necessary, in a covered container.
• VARIATIONS on the flavor of these butter cookies are limitless. Here are a few suggestions:.
• Butterscotch cookies: Substitute brown sugar for half or more of the white sugar, or simply add 1 tablespoon of molasses along with the egg.
• Citrus cookies: Omit the vanilla, and add 1 tablespoon of lemon or orange juice and 2 teaspoons grated lemon or orange rind along with the egg. A couple of tablespoons of poppy seeds can also be added.
• Chocolate chip cookies: Stir in about 1 cup of chocolate chips. (The butterscotch variation is good with chocolate chips.).
• Other chunky cookies: To the finished batter, add about 1 cup of M& M's (or similar candy), roughly chopped walnuts, pecans or cashews, slivered almonds, raisins, coconut, dried cherries or cranberries. Or combine any chunky ingredients you like.
• Ginger cookies: Add 1 tablespoon ground dried ginger to the dry ingredients. For even better flavor, add 1/4 cup minced crystallized ginger to the batter by hand (this works well in addition to or in place of the ground ginger).
• Spice cookies: Add 1 teaspoon ground cinnamon, 1/4 teaspoon each ground allspice and ground ginger and 1 pinch ground cloves and mace or nutmeg to the dry ingredients.
• Or you can make rolled cookies by freezing the dough for 15 minutes or refrigerating it for at least 1 hour. Working half the dough at a time, roll it out on a lightly floured surface; the dough will absorb some flour at first but will soon become less sticky. Do not add more flour than necessary. Roll about 1/4 inch thick, and cut with cookie cutters; decorate as you like. Bake as above, reducing the cooking time to 8 to 10 minutes.