Brown the butter and mix with the sugars

• Brown the butter in a saucepan.
• While still very warm (almost hot but not boiling), pour it directly over the brown sugar and granulated sugar.
• Whisk until smooth and glossy.

Add egg and vanilla

• Let the mixture cool for 1–2 minutes.
• Whisk in the egg and vanilla until fully combined.

Make the cookie dough

• Fold in the flour, baking soda and salt until just combined.
• Fold in the chocolate chips and chunks.

Shape the dough

• Scoop about 3–4 oz of dough per cookie.
• Flatten each piece slightly.

Assemble the s'mores stacks

• Place a piece of graham cracker, a piece of dark chocolate and a marshmallow on the baking sheet.
• Place the flattened cookie dough over the top, leaving a small hole so the marshmallow can seep through.

Bake the cookies

• Arrange the cookies on a parchment-lined baking sheet with plenty of space between them, as they spread.
• Bake at 350 °F (175 °C) until the edges are golden and the centers still soft, checking from 12 minutes.

Spread the marshmallow

• While the cookies are still warm, gently spread the marshmallow around the opening if it hasn't spread enough.
• This gives the melted, gooey look on top.

Decorate with ghost faces

• Draw a little ghost face onto each marshmallow with the edible food-safe marker.
• Place a decorated marshmallow on top of each warm cookie.