Make the cookie dough

• Cream the softened butter with the granulated sugar and brown sugar.
• Beat in the egg and vanilla extract.
• Whisk together the flour, baking soda, salt and cornstarch, then mix into the wet ingredients until a dough forms.

Build the s'mores

• Place a marshmallow and pieces of milk chocolate bar between two graham crackers to make each s'more.
• Take about 2 tbsp of dough, flatten it with your palms and wrap it completely around each s'more.
• Press a few milk chocolate chips into the outside of each dough ball.

Freeze the cookies

• Arrange the wrapped cookies on a tray with space between them, as they spread while baking.
• Freeze while the oven preheats.

Bake

• Preheat the oven to 175 °C (350 °F).
• Bake the cookies until set and lightly golden.

Fix the edges and cool

• While still hot, run something circular around each cookie to neaten the edges.
• Let cool on the tray before serving.