Melt the butter in a large mixing bowl until smooth. Allow to cool, then whisk in white sugar, brown sugar, egg, and vanilla until lump-free.

Sift together flour, cornflour, baking soda, and salt over wet ingredients. Fold gently, forming a soft dough.

Wrap the dough in plastic wrap and refrigerate for about 30 minutes. Preheat oven to 170°C (340°F) and line a tray.

Scoop about 2 tablespoons of dough, roll into balls, and place on the lined tray, spacing 2 inches apart. Flatten slightly.

Bake for 12-15 minutes. Look for golden edges and soft centers. Avoid overcooking.

Press two Maltesers into each warm cookie center as soon as they come out of the oven.

Melt dark chocolate, pipe eight legs on each cookie, flanking the Maltesers.

Decorate with white icing to create googly eyes above each Malteser.