3 1/2 to 4 pounds boneless pork shoulder (butt)
1 rounded tablespoon superfine sugar
Juice of 1/2 lemon
2 tablespoons white balsamic or white wine vinegar
1/4 cup EVOO
Salt and pepper
8 ounces cabbage, very thinly sliced in a food processor or with a mandoline
1 bulb fennel, very thinly sliced in a food processor or with a mandoline, plus a handful of chopped fronds
4 ciabatta or other crusty sandwich/sub rolls, crisped in the oven and split
Sea salt and coarsely ground pepper
Cloves from 1 head garlic, chopped
Leaves from 5 or 6 sprigs fresh rosemary, finely chopped
2 tablespoons fennel seeds
EVOO, for liberal drizzling
4 medium onions, peeled and cut into eighths with the root end intact
1 cup dry white wine
Chicken stock, for reheating (if this is a make-ahead)
Preheat the oven to 375°F.
Roast the pork: Have the butcher butterfly the meat for you or with a very sharp knife, split the shoulder to open like a book, each side 1 to 1 1/2 inches thick. Heavily sprinkle the meat with sea salt, pepper, garlic, rosemary, and fennel seeds. Roll up the meat and tie with kitchen twine. Slather with EVOO and sprinkle with salt and pepper. Dress the onions with EVOO, salt, and pepper and scatter in a baking dish. Set the meat on top and roast 1 hour.
Douse the pan with the wine and return to the oven. Roast until the pork is very tender and the internal temperature reaches 145° to 150°F, another 1 to 1 1/2 hours. If serving this on Cook Day, let stand 15 minutes before slicing.
Make-ahead: Cool, cover, and refrigerate.
Night of: Slice the roast pork. Reheat the pork and onions in a shallow pan of warm chicken stock to heat through.
Make the slaw: In a large bowl, combine the sugar, lemon juice, vinegar, and EVOO and season with salt and pepper. Add the cabbage, fennel, and fennel fronds and toss.
To serve, pile the meat on rolls with warm onions and fennel slaw on top.