375g dark chocolate melts
2 1/2 cups pure icing sugar
1 tablespoon vegetable oil
2 tablespoons milk
1/4 teaspoon peppermint essence
1. Grease a 6cm-deep, 20cm square cake pan. Line base and sides with baking paper, allowing a 3cm overhang on all sides. Place half the melts in a microwave-safe bowl. Microwave on high for 1 to 2 minutes or until smooth, stirring with a metal spoon every 30 seconds.
2. Pour chocolate over base of prepared pan. Refrigerate for 15 minutes or until set.
3. Sift icing sugar in a microwave-safe bowl. Stir in oil and milk to form a thick paste. Microwave on high for 2 to 3 minutes, or until smooth, stirring every 30 seconds. Stir in peppermint essence. Set aside for 2 minutes to cool slightly. (If mixture is too thick, add 1 tablespoon milk).
4. Pour peppermint mixture over chocolate in pan, spreading with a spatula. Refrigerate for 15 minutes or until just set. Place remaining chocolate in a microwave-safe bowl. Microwave on high for 1 to 2 minutes or until smooth, stirring with a metal spoon every 30 seconds.
5. Pour chocolate over peppermint layer. Refrigerate until set. Lift chocolate from pan and, using a warm knife, cut after-dinner mints into squares.