preheat oven to 375 degrees f.place flour,cocoa,baking powder and baking soda in medium bowl;stir to combine.set aside.
beat margarine,brown sugar and 1/2 cup granulated sugar with electric mixer at medium speed until light and fluffy;beat in eggs and vanilla. gradually add flour mixture and 1/2 cup of pecans. beat at low speed,scraping down sides of bowl occasionally.refrigerate dough,covered,15 minutes or until firm enough to roll into balls.
place remaining 1/2 cup pecans and 1 tablespoon of sugar into shallow dish.roll tablespoon of dough around 1 caramel candy,covering completely;press one side into nut mixture.place,nut side up,on ungreased cookie sheet.repeat with each additional candies,placing 3 inches apart.
bake 10 to 12 minutes or until set and slightly cracked.let stand on cookie sheet 2 minutes.transfer cookies to wire rack;cool complete.
place white chocolate pieces in small resealable plastic freezer bag;seal bag.microwave at medium (50%)power for 2 minutes.turn bag over;microwave again for 2 to 3 minutes or until melted.knead bag until chocolate is smooth.cut off tiny corner of bag;drizzle white chocolate onto cookies.let stand until white chocolate is set,about 30 minutes.