Preheat oven to 180C (350F). Line two large baking trays with parchment paper.

In a large mixing bowl, cream together the butter, brown sugar, and granulated sugar until light and fluffy.

Beat in the egg and vanilla until smooth.

In another bowl, whisk together flour, baking soda, baking powder, and salt.

Mix the dry ingredients into the wet until just combined.

Fold in most of the Reese’s Pieces and all of the chocolate chips, saving a few for topping.

Scoop tablespoon-sized portions (around 40 g each), roll into balls and place on prepared trays about 2 inches apart.

Bake for 10–11 minutes until the edges are set but the centres look slightly soft.

Remove from oven and immediately press a few sugar eyes and reserved Reese’s Pieces on top.

Leave to cool on the tray for 10 minutes before transferring to a wire rack.