Heat a frying pan over a low heat and gently toast the allspice berries, black peppercorns, cinnamon pieces and coriander seeds, shaking the pan occasionally. Remove from the heat when the aroma of the spices has been released.
Add the toasted spices to a mortar and pestle and crush until it forms a grainy powder.
Place the spices into a food processor (I used my Optimum Thermocook) and blitz until a paste has formed.
This can be stored in a jar in the fridge for up to two weeks, or divide into portions and freeze for up to 3 months, defrosting when needed.
for the pulled pork
The night before, combine half the jerk marinade with the coffee granules dissolved in the hot water and the orange juice. Massage deep into the scored flesh of the rolled pork shoulder and place into your slow cooker pot, cover, and leave to marinade in the fridge until the next morning.
Cook the pork on low for 8-10 hours. When cool enough to handle, remove the meat from the pot, shred with two forks, cover and set aside. Reserve any juices in the pot.
Just before you are ready to serve, heat the remaining jerk marinade in a small saucepan until the spices release their aroma. Mix with the orange juice and any juices at the bottom of the slow cooker pot and bring to the boil. Leave to simmer for a few minutes to reduce.
Pour the dressing over the pulled pork, tossing to make sure everything is well coated. The pork can be frozen at this stage, or chill it for a few days if you've got a BBQ coming up and reheat on the BBQ.
To serve, arrange the watercress on a platter and scatter with the cubed watermelon seasoned generously with sea salt (use a lot!). Add the pulled pork and gently toss together.