Preheat your oven to 180°C (160°C fan) or 350°F. Line a baking tray with baking paper.
Beat together the butter, brown sugar and granulated sugar until light and fluffy.
Mix in the pumpkin purée, egg and vanilla extract. If you want bright orange cookies, this is the time to add the food colouring.
In another bowl, whisk together the flour, bicarbonate of soda, pumpkin spice and salt.
Slowly add the dry mixture into the wet ingredients until just combined.
Fold through the chocolate chips, marshmallows and biscuit pieces.
Scoop the dough onto your tray, leaving space between each one.
Press a few extra marshmallows, chocolate chips or biscuit pieces into the top of each cookie.
Bake for 15 minutes, until the edges are golden but the centres are still soft.
Let them cool on the tray before digging in.