Preparation - Unwrap the baking chocolate squares and place each kind of chocolate in separate, microwave-safe bowls. Melt each bowl of chocolate, one at a time.... microwave on full power for one minute, stir, then microwave for 30 second intervals until the chocolate is all melted. (Be sure to stop and stir every 30 seconds to prevent scorching the chocolate.) Stir 1/2 cup of the chopped pecans into each bowl of melted chocolate. Alternately spoon the melted chocolate/pecan mixtures onto a parchment paper lined cookie sheet. Using a table knife, very gently swirl the chocolate mixtures together for a marbled look. Allow the chocolate to harden completely, then break or cut the marbled bark into desired size pieces.