Pre-heat your oven to 180C Fan/200C/400F/Gas Mark 6, line your baking tray(s) with baking paper
Ideally using a stand mixer with the paddle attachment, mix the butter, caster sugar and light brown soft sugar together until fluffy and paler in colour. This will take 3-5 minutes in an electric mixer (I use speed 3)
Add the egg and vanilla extract and mix in
Add the plain flour, cocoa powder, baking powder, bicarbonate of soda and salt (you can mix them together in a separate bowl first if you like) and mix them in until just combined
Then mix in the milk chocolate chips briefly, just to evenly distribute them
Divide the dough into portions, I weighed the dough out to make each cookie an equal size. Place the dough balls onto lined baking trays, leaving space (at least 2") between them to spread. If you don't have enough baking trays, keep the dough in on the counter and bake the cookies in batches
Bake the cookies for 12 minutes, then leave to cool on the trays for at least 10 minutes before moving to a cooling rack
While they are baking, make the ganache by placing the dark chocolate, butter and double cream into a microwave safe bowl. Microwave for 20 seconds on high (I used a 900W microwave). Then stir well. Microwave in 10 second blasts, stirring between each one, until the ganache is smooth and glossy. Set it aside to cool and thicken
Make the green buttercream by mixing together the butter and icing sugar, then add the vanilla, milk and green food colouring, and mix until smooth and the desired shade is achieved. For best results use a stand mixer with the paddle attachment or a handheld electric mixer. Put the green buttercream into a piping bag and snip off a small section at the end with scissors
To decorate the cookies, spread a layer of ganache over them using the back of a teaspoon, add a fondant pumpkin, then sprinkle on the crushed Oreo crumbs, finally pipe on some vines with the green buttercream
Store leftovers in an airtight container and eat within 3 days
Video
Notes
Make sure all your ingredients (particularly the butter and egg) are at room temperature before you start baking.
I used unsalted butter for this recipe, a baking spread will work but butter has a lower water content so the dough will be less sticky.
I recommend using light brown soft sugar for delicious flavour and a more gooey cookie, but you can replace it with caster sugar if you can't get hold of light brown soft sugar.
I used milk chocolate chips in the cookies, you could use dark or white chocolate, or omit them entirely if your prefer.
Instead of chocolate ganache, you could use Nutella to stick the decor to the cookies.
I used crushed Oreos for the "soil", but chocolate bourbon biscuits would also work well.
I made the little signs from wooden lollipop sticks that I broke in half, wrote on with pen and stuck together with some double sided tape. You don't have to make the signs, and if you do please be careful of splinters or small fragments of wood left in the food.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.