Preheat the oven to 180'C / Gas 4 and line two baking trays with baking paper. Set aside.

Add the Stork, sugar and salt to a large mixing bowl and cream until pale using either a wooden spoon or a handheld mixer. 

Add the egg white, flour, cocoa, vanilla essence and xantham gum. Using your hands bring the mixture together. It may appear a bit crumbly at first but keep kneading with your hands until it comes together in a dough. You should be able to scrunch it in your fist and it doesn't crumble. If it's too crumbly, add the water 1/2 tsp at a time.

Tip dough mix out onto worktop and roll out to around 5mm-1cm thick (see note 1) and using a 2.5-inch cookie cutter, cut out 10 shapes. Place evenly on the baking tray (allow a little room, but they shouldn't spread) and prick the tops with a fork. Bake for 9-10 minutes, remove from the oven and cool completely on a cooling rack.

Place the marshmallows into a bowl and microwave for 45 seconds. Stir with a spoon and then spoon into a piping bag before they cool too much. Set aside for 2-3 minutes to cool.

Pipe the marshmallow onto 5 of the biscuits. (You want this to be about 1cm from the edge and fairly thick, so that when you put the second biscuit on top, the marshmallow doesn't escape everywhere!). Leave for around 30 seconds to cool slightly, then place 1/2 tsp of jam on top. (See note 2)

Place the second biscuit on top and leave to cool at room temperature for five minutes. Meanwhile, melt the chocolate in the microwave or in a bowl over hot water.

Use the 'dip and roll' technique to dip the wheels, side on, into the melted chocolate and then roll them, so that the chocolate coats and seals the outside. Place back onto a wire baking tray. Once you've done this with all the biscuits, use a knife or spoon to coat the tops of each wheel evenly with the remaining chocolate. (see note 3)

Cool in the fridge for an hour, and then these are ready to be enjoyed!