For the corned beef
Place the corned beef in a Dutch oven. Pour in the beer and enough water to cover the meat by 1 to 2 inches. Wrap the coriander seeds, bay leaves, chile, and allspice in a square of cheesecloth, tie with butcher’s twine, and throw the spices into the pot. Bring to a boil, then reduce the heat to a simmer, cover the pot, and cook for 2 hours. Check the beef by inserting a knife into the thickest part. If it shows no resistance, the meat is tender. To make sure, cut off a bit and taste it. If it is not tender, continue to cook, checking every 30 minutes. Remove the beef from the pot and cover loosely with aluminum foil to keep warm.
Add the potatoes, onions, turnips, parsnips, carrots, and cabbage to the pot, cover, and cook at a slow boil for 20 minutes, or until tender. Return the beef to the pot to rewarm for 2 to 3 minutes. Discard the spice bag. Cut the meat across the grain into 1/4-inch-thick slices and arrange on a platter with the vegetables. Serve with the Dill Pickle–Horseradish Cream and Guinness-Mustard Sauce.
Leftovers are great in Reuben-type sandwiches or corned beef hash.