Preheat oven to moderate (350°). Grease 15 x 10 x 1-inch jelly-roll pan. Beat together butter and sugar in large mixer bowl until well mixed. Beat in egg and vanilla. Stir in flour until well blended. Spread dough evenly over bottom of prepared pan. Bake in preheated moderate oven (350°) for 25 minutes or until lightly browned on top. While cookie crust is baking, melt chocolate in top of double boiler over hot water. Remove cookie crust from oven. Spread chocolate in an even layer over top. Set pecan halves in chocolate or sprinkle chopped pecans over top. Cut into bars, about 1x1-3/4 inches, while still slightly warm. Store cookies in cool place. Nutrient Value Per Cookie: 79 calories, 1 g protein, 5 g fat, 8 g carbohydrate, 32 mg sodium, 12 mg cholesterol. cook 015