Line a 17 x 12 inch jelly roll pan with parchment paper. Break each chocolate bar into 8 equal pieces.(You will have 48 pieces total.) Arrange in a checkerboard pattern in jelly-roll pan , alternating white and dark chocolate.(Pieces will touch.)
Bake at 225* for 5 minutes or just until chocolate is melted. Remove pan to a wire rack. Swirl chocolates into a marble pattern using a wooden pick. Sprinkle evenly with toasted pecans and salt.
Chill for 1 hour or until firm. Break into pieces. Store chocolate in an airtight container in refrigerator up to 1 month.