Line a deep 9 x 12 inch glass dish with baking paper (parchment paper) making sure to line the sides. Then spray the paper lightly with oil.
Next, make the gelatine mixture. In the bowl of your stand mixer, add the cold water then sprinkle the gelatine powder on top. With the whisk attachment on, stir to combine the let it sit to bloom.
Add the syrup ingredients - water, sugar, cocoa powder, corn syrup, honey, and salt to a large saucepan with high sides.
Over medium-high heat, stir and bring to a rolling boil.
Using a candy thermometer, bring the mixture to 116˚C (240°f ) or softball. Do not stir the mixture.
Once the syrup mixture has reached the temperature (softball stage), turn off the heat and let it cool to around 99˚C (210˚F).
With the whisk attachment on, turn the stand mixer onto low speed and gently pour the syrup into the gelatine mixture.
Once all the syrup mixture is in, add the vanilla and then gradually increase the speed to high and whip until it thickens and soft peaks form.
Pour the marshmallow mixture into the prepared dish.
Smooth out the top of the marshmallow and then sprinkle the chocolate chips on top.
Set aside for 8 to 10 hours or overnight.
Once set, remove the chocolate marshmallow from the dish by lifting the paper out of the dish.
Mix the cocoa powder and icing mixture together and sprinkle some on top of the marshmallows.
Cut into 1 - 2' strips, then into 1 - 2' cubes. Clean the knife between cuts for a smooth slice.
Nutritional information is an estimate and provided as a courtesy. The values may vary according to the ingredients and tools that are used. Please use your preferred nutritional calculator for more detailed information.