21/4 pounds lean, boneless pork shoulder
2 teaspoons coarse salt
1 tablespoon crushed black peppercorns
2 bay leaves, crushed to a powder
1/2 teaspoon crushed fennel seeds
2 sprigs thyme
2 cups good-quality olive oil
1 small head garlic, halved
1 small red onion, sliced paper-thin
2 1/2 tablespoons red-wine vinegar
Toasted, sliced baguette, for serving

Trim away all fat, sinew and membrane from the pork. Cut meat into 2-inch chunks. In a small bowl, stir together the salt, peppercorns, bay leaves, fennel and thyme. Put meat and spicing mixture in a large, sealable bag and massage seasonings into pork. Squeeze out all air, seal tightly and refrigerate for at least 6 hours or overnight.

Heat oven to 250 degrees. Without draining meat, squeeze pieces into a medium ceramic or enameled cast-iron casserole in a single layer. Pour on the olive oil to cover completely. Cover with a sheet of crumpled parchment and a lid, set over very low heat and cook until oil comes to a boil, 30 to 45 minutes.

Add the halved head of garlic, transfer casserole to oven and cook for 2 1/2 hours longer. Check that oil bubbles only a little; meat should not brown. To test if pork is ready, scoop out one piece and tap it lightly; it should break into smaller chunks and be a soft pink color. Remove from oven and let stand until completely cool. Refrigerate for up to 5 days. (Be sure pork is completely covered in oil; add additional fresh oil, if necessary.)

Before serving, reheat pork slowly. At the same time, soak the red onion in the vinegar for 30 minutes. Drain pork in a colander set over a bowl to catch juices; discard garlic and thyme.

Set bowl of juices aside to settle and break up pork cubes roughly with a fork. When juices have settled, pour off olive oil floating on top (you can save this to use for cooking; it's delicious), reserving about 1/4 cup to 1/2 cup. Stir meat juices into meat along with just enough olive oil to make shreds shiny and slightly sticky. Taste and correct seasoning. Spoon meat mixture onto warm, toasted bread and top with a little pickled onion.

Makes 8 servings.