Add your oats to a blender with your water and leave the oats to sit and soak for at least 10 minutes, then blend thoroughly until all the oats have broken down.
Top a bowl or jug with a tea towel or a muslin cloth, securing it with a rubber band or a piece of string, then slowly pour the oat milk from your blender into your bowl or jug, allowing the milk to drain out, leaving the oat residue behind.
Once your milk is all poured over, remove whatever is securing your cloth over the bowl/ jug and squeeze out as much milk as possible, discarding what’s left of the oats.
Pour your milk into a medium saucepan on medium-low heat, then add your chocolate, splash of double cream, vanilla and a pinch of salt.
Cook on medium-low heat, whisking and allowing the chocolate to melt.
Cook for between 5-10 minutes, and once it’s thickened to the texture you like, reduce the heat to low.
Whisk your double cream until it’s thick enough to spoon on top of your hot chocolate, then pour your hot chocolate between 2 mugs and top with your whipped cream, some crumbled biscuits and some grated dark chocolate.