1. Preheat oven to 180°C.
2. Grease a 18cm x 28cm slice pan; line base and 2 long Beat the margarine, sugar and yolk in a small bowl with an electric mixer until light and fluffy.
3. Stir in sifted flour and Kellogg's® Rice Bubbles®; mix well.
4. Using fingers, press mixture evenly over base of prepared pan.
5. Bake, uncovered, in oven about 15 minutes or until browned lightly.
6. Cool slightly.
7. Combine remaining ingredients in a medium bowl.
8. Spread evenly over cooled base using back of a metal spoon; refrigerate until firm.
9. Cut into squares.

Tip: For an extra treat, sprinkle chocolate mixture with chocolate sprinkles or hundreds and thousands or coloured snowflakes before refrigeration. Store in an airtight container in the fridge.