Step 1

Using an electric mixer, beat butter, sugar and vanilla together for 5 minutes or until light and fluffy. Add egg. Beat until just combined. Stir in flour, in 2 batches, until just combined. Stir in M&M’s. Turn dough out onto a clean surface. Knead into a ball.

Step 2

Roll and shape dough into a 30cm-long log. Wrap in baking paper and freeze for 30 minutes or until firm (see note).

Step 3

Preheat oven to 180C/160C fan-forced. Line 3 large baking trays with baking paper.

Step 4

Unwrap cookie log. Using a serrated knife, cut into 1cm-thick slices. Place, 3cm apart, on prepared trays. Bake, 1 tray at a time, for 10 to 12 minutes or until edges are just starting to turn light golden. Stand on trays for 5 minutes. Transfer to a baking paper-lined wire rack to cool completely. Serve.