1. Line cookie sheet with wax paper.
2. Place chocolate chips in medium microwave-safe bowl. Microwave at MEDIUM (50%) 30 seconds; stir. Continue microwaving at MEDIUM in 15 second increments, stirring after each heating, until chips are melted and smooth when stirred. Set aside. Repeat melting procedure with white chips.
3. Pour melted chocolate onto prepared cookie sheet; spread to about 1/2-inch thickness. Drop melted white chips by teaspoonfuls onto melted chocolate; swirl with knife for marbled effect. Gently tap cookie sheet on countertop to even out thickness. Sprinkle pecan pieces over surface. Repeat tapping cookie sheet on counter until candy is desired thickness.
4. Refrigerate about 30 minutes or until firm. Break into pieces. Store in cool, dry place. About 3/4 pound candy.