For the Brine:
6 Cups water
2 Cups lager beer
1-1/2 Cups Coarse Kosher Salt
1 Cup (packed) golden brown sugar
1/4 Cup Pickling Spices
1, 6- to 8-pound flat-cut beef brisket, trimmed, with some fat remaining
For the Corned Beef and Vegetables:
1 12-ounce bottle Guinness beer, or any other stout or porter [dark] beer
4 Bay Leaves
1 Tbsp Coriander Seeds
2 Whole Allspice Berries
1/3 tsp Chile de Arbol, Crushed
12 baby turnips, trimmed, or 3 medium turnips or rutabagas, peeled and quartered
8 unpeeled medium white-skinned or red-skinned potatoes (about 3 pounds)
6 medium carrots, peeled
4 medium onions, peeled, halved through root ends
2 medium parsnips, peeled, cut into 2-inch lengths
One 2-pound head of cabbage, quartered
Add some spicy mustard or horseradish to really set off the flavors!
To make the brine:
Pour 6 cups water and lager beer into large deep roasting pan. Add coarse salt; stir until dissolved. Add sugar; stir until dissolved. Stir in pickling spices. Pierce surface of the brisket all over with the tip of a small sharp knife. Submerge brisket in briny liquid, then top the brisket with heavy platter to weigh it down. Cover and refrigerate at least 6 hours, but up to 4 days.
Remove brisket from brine. Rinse with cold running water. Wrap corned beef in plastic, cover with foil, and refrigerate until you’re ready to cook [up to two days ahead of time].
To make the corned beef and vegetables:
Place corned beef in very large, wide pot. Add stout beer and enough water to cover the brisket by 1 inch. Wrap cheesecloth or a small drawstring muslin bag around bay leaves, coriander seeds, allspice, and chile de arbol, enclosing completely, and, if using cheesecloth, tie with kitchen string to secure.
Add spice bag to the pot with the beef and beer; bring to boil. Reduce heat to medium-low, cover, and simmer until beef is tender, about 2-1/4 hours. Transfer corned beef to large baking sheet.
Add the vegetables to the liquid in the pot; bring to a boil once again. Reduce heat to medium and boil gently until all the root vegetables are tender, about 25 minutes.
Using a slotted spoon, transfer vegetables to the baking sheet with beef. Return corned beef to pot and rewarm 5 minutes. Remove and discard spice bag.
Cut beef against grain into 1/4-inch thick slices. Arrange beef and vegetables on platter.
Serve with Horseradish Cream (horseradish and sour cream) and Guinness Mustard.