Place can of coconut milk in the fridge overnight to chill.
Place chicken, peppercorns, celery, onion, carrot, bay leaves and rosemary in a large saucepan and cover with cold water. Bring to the boil, then reduce heat to low and simmer gently for 1 hour and 20 minutes. Remove chicken and set aside for 30 minutes to cool.
Remove chicken from bones and skin, then shred meat with 2 forks.
Carefully turn the can of chilled coconut milk upside down, then use a can opener to remove the bottom of the can. Drain off the liquid and scrape the thick coconut cream into a bowl. You should have about 1/3 cup coconut cream.
Add the lemon juice, vinegar and sea salt. Stir until smooth. Combine 2 cups chicken, Henley’s “sour cream”, parsley, spring onions and slivered almonds into large bowl, and mix well. Season with salt and pepper.
Evenly spread filling over 6 of the bread slices. Top with remaining bread slices and press down gently. Cut each sandwich into 4 squares. Top each square with a slice of cucumber and garnish with parsley.