Mix the chestnut purée with the chestnut paste and oat milk in a saucepan without heating. At the same time, weigh the dry ingredients together (Pectin NHX, Natur Agrum, Warmtex and sugar). Whisk the dry ingredients into the liquid, then bring to the boil, stirring constantly. Pour the mixture over the coconut oil, cocoa butter and rum, then blend with a hand blender to perfect the emulsion. Cool quickly before use.