Slightly deep tray or square cake panaprox. 30x20x5cm (12x8x2 in) oiled and lined with baking paper
Silicone spatula - wiped with oil
Oil your pan or cake tin. Line with baking paper and oil again. Oil a silicone spatula.
Put the cold water in the bowl of your stand mixer and sprinkle the gelatine on top. Let it swell or 'bloom'.
Put the remaining water, sugar, corn syrup, golden syrup, treacle and rum in a medium deep saucepan. Clip on a sugar thermometer and bring to the boil. Keep boiling until it reaches 120C | 248F (firm ball stage).
Meanwhile add the spices to the gelatine and whisk together at high speed.
When sugar reaches the right temperature slowly add it to the gelatine - down the side of the mixing bowl - while whisking at slow speed initially and increasing to high speed once all syrup is added. Keep whisking for several minutes (can take up to 10-15 mins) until the mixture is thick, glossy and bubblegum-like.
Stir in the orange zest and grated chocolate. Spoon the marshmallow into the prepared pan and spread evenly. Dust with the coating and leave to set at room temperature for 2 hours (or longer). (I used a small amount of marshmallow spread thinly of a second tray to create the small gingerbread mallows).
Use a greased pizza wheel or a sharp knife to cut the marshmallows into cubes. Or use greased cookie cutters to create shapes. Toss them in the coating so that they are covered all over (otherwise they will dry out). Store in an airtight container for up to two weeks.
If you can't find golden syrup you can use all light corn syrup or liquid glucose (160g or 1/2 cup). Do not be tempted to get heavy handed with the rum - too much and the mallows will not set.