Zest the mandarins and slice in half
Carefully juice the mandarin halves using a reamer
Use a spoon to scoop out any remaining flesh from the mandarin halves
Add heavy cream, sugar, salt, zest and turmeric (if using) to a saucepan over medium heat
Bring to a boil, then reduce heat slightly and let simmer for 5-6 minutes, stirring often to prevent burning
Strain through a fine mesh sieve and discard the zest
Whisk in the mandarin juice until the mixture thickens slightly
Arrange the mandarin halves on a plate or platter and pour in the posset mixture
Refrigerate for at least 3 hours (until set) or up to overnight before serving
