Sift the 1/3 cup cocoa powder and cinnamon together and set aside.
Grease and line a 20cm x 30cm x 3cm slice tray.
Sift a small amount of the spiced cocoa powder over the base of the lined tray and set aside. Try and coat as much of the base as possible.
Place the boiling water and cocoa powder into the bowl of a stand mixer. Whisk to remove any lumps.
Add the gelatine, vanilla extract and salt to the water and cocoa. Stir gently to combine.
Place the sugar, rice bran syrup and water in a medium saucepan over a medium - high heat.
Without stirring, bring the sugar mixture to the boil. Continue to boil until the syrup reaches 115C on a candy thermometer. This will take approximately 15 minutes.
Turn the stand mixer onto low and quickly pour the sugar syrup into the bowl. Continue to mix on low until the gelatine mixture has melted and no lumps are visible.
Turn the mixer up to medium high and whisk for approximately 10 minutes. The mixture will start to foam and thicken. It is ready when the marshmallow is the consistency of soft serve ice cream.
Pour the mixture into the prepared pan and spread out with a spatula. Sprinkle with some of the spiced cocoa powder.
Allow the marshmallow to set at room temperature for approximately 6 hours, or until firm. I leave mine overnight.
Cut into desired shapes and toss the cut marshmallow in the spiced cocoa powder. Shake off excess cocoa powder and store in an airtight container.