METHOD:For the Sachet:
Combine the juniper berries, black peppercorns, bay leaf, rosemary, and thyme into a sachet.For the Rillettes:
Combine the pork shoulder with the salt, garlic cloves, and sachet. Place in the refrigerator for about 8 hours to cure.
Melt the duck fat. Preheat the oven to 350°F. Put the pork and livers in a large pan. Add the duck fat until the meat is submerged. Place in the oven and simmer for 2 hours or until tender. Cool the meat to room temperature and strain the duck fat. Remove the sachet. Shred the meat by hand, breaking it up into small pieces. Adjust the seasoning. Pack the meat into a terrine mold leaving ¾-inch from the top of the terrine. Transfer to the refrigerator and chill. Heat the strained duck fat and pour it through a chinois on top of the rillettes.To Assemble and Serve:
Cut ½-inch thick slices of the terrine, remove the duck fat cap, and serve. To preserve the rillettes for up to a month, melt the fat cap and add it back to the rillettes to seal until needed again.