TO MAKE WHITE CENTER, combine corn syrup and cream in a small saucepan. Bring to a boil. Remove heat and add white chocolate. Leave stand few minutes until white chocolate melts and, if necessary return to low heat. Pour mixture into a medium bowl lined with foil. Chill until firm. Form mixture into 6 balls. Freeze until firm.

TO MAKE CHOCOLATE COATING, melt butter in a small saucepan on low heat. Add semisweet chocolate; remove heat. Stir until smooth. Add cream and Grand Marnier. Chill until slightly firm. To assemble truffles, divide semisweet chocolate mixture into 6 balls. Flatten each ball. Wrap around white chocolate ball. Roll between hands to form an even surface.

Roll balls in cocoa. Freeze until firm. Wrap each ball in plastic wrap and then in foil. Store in freezer up to 8 weeks.

TO SERVE, CUT EACH FROZEN BALL IN 1/2, USING A KNIFE DIPPED IN BOILING WATER. DIVIDE EACH 1/2 INTO 3 WEDGES. Place in small paper cases, white side up. Makes 36 truffles.

Chocolates & Petits Fours.