Preheat your oven to 180°C (400°F) and line two baking trays with parchment paper.

In a mixing bowl, cream together 125g softened unsalted butter with 125g light brown sugar and 75g caster sugar until the mixture is light and fluffy, about 3-5 minutes.

Beat in 1 large egg and 1 teaspoon of vanilla extract until fully incorporated.

In a separate bowl, whisk together 215g plain flour, 35g cocoa powder, ½ teaspoon baking powder, ¼ teaspoon bicarbonate of soda, and ¼ teaspoon salt until well-mixed.

Gradually add this dry mixture to the wet dough, blending until just combined.

Fold in 200g milk chocolate chips to ensure an even distribution throughout the cookie dough.

Divide the dough into equal portions, roll each portion into a ball and gently flatten it before placing on the lined baking trays.

Bake the cookies for 12 minutes, or until they appear set and slightly risen.

Allow the cookies to cool on the trays for at least 10 minutes before transferring them to a wire rack to cool completely.

In a microwave-safe bowl, combine 100g dark chocolate, 15g unsalted butter, and 100ml double cream. Heat until all the ingredients melt together smoothly.

Stir until glossy, then set aside to cool at room temperature until the ganache thickens slightly.

In a bowl, whip 25g softened unsalted butter with 50g icing sugar until creamy, then add ⅛ teaspoon vanilla extract, ¼ tablespoon of milk, and green food coloring to achieve a smooth consistency.

Spread a layer of thickened chocolate ganache on top of each cookie, sprinkle crushed Oreos over the ganache, and place fondant pumpkins on top.

Use the green buttercream to pipe decorative vines that twist around the pumpkins.