Grease a 9×13-inch metal baking pan, then line with foil, leaving a 2-inch overhang on both ends, and grease foil. Follow recipe for basic cookies (do not chill the dough), then press dough evenly onto the bottom of the baking pan, using plastic wrap on top to prevent the dough from sticking to your fingers. Chill until firm, about 20 minutes.

While crust chills, put oven rack in middle position and preheat oven to 375°F (190°C).

Bake crust until golden brown, about 30 minutes. Remove from oven and cool in pan on a rack for 20 minutes. (Leave oven on.)

While the crust cools, make the caramel pecan topping.

Cook sugar in a 2½- to 3-quart heavy saucepan over moderate heat, undisturbed, until it begins to melt. Continue to cook, stirring occasionally with a fork, until sugar is melted to a deep golden caramel. Tilt pan and carefully pour in whipped topping (caramel will harden and steam vigorously). Cook over moderately low heat, stirring, until caramel is dissolved. Remove from heat and stir in margarine, vanilla, salt, and pecans.

Immediately spread topping over cooled crust and bake until bubbling, about 20 minutes. Cool completely in pan on rack for about two hours.

Cut into 2-inch triangles, diamonds, or squares (for neat slicing, run a heavy knife under hot water, then wipe dry).