2poundsuncooked corned beef brisketabout 1 small, rinsed, trimmed if fatty, spice packet discarded if included
4sprigs flat-leaf parsley
3bay leavestorn
1tablespoonblack peppercorns
1tablespooncoriander seeds
1tablespoonyellow mustard seeds
1large onionpeeled, halved through root
2large russet potatoespeeled, halved crosswise
For Hash:
1/4cupchopped fresh flat-leaf parsleyplus more for serving
Kosher saltfreshly ground pepper
2tablespoonsolive oil
1teaspoondistilled white vinegar
4large eggs
For Serving:
Fresh chiveschopped
Flat-leaf parsleychopped
Instructions
For Corned Beef:
Place corned beef in a large Dutch oven or other heavy pot (at least 5 quarts) and add water to cover by 1". Add parsley sprigs, bay leaves, peppercorns, coriander seeds, and mustard seeds. Bring to a boil; reduce heat, cover, and simmer, skimming surface often and adding more water to pot as needed to keep meat submerged, until corned beef is tender, 3-1/2 to 4 hours.
Add onion and potatoes to corned beef in pot, cover and cook until vegetables are very tender, 20 to 25 minutes. Remove onion and potato from pot. Let cool; wrap separately and chill.
Let corned beef cool in cooking liquid. Transfer corned beef to an airtight container and add as much cooking liquid as will fit (at least 1 cup). Cover and chill. Discard any remaining aromatics and cooking liquid.
For Hash:
Remove corned beef from cooking liquid and shred enough to measure 2 cups. Use any remaining corned beef for sandwiches or snacking.
Preheat oven to 200°F. Chop the cooked onion and cut cooked potato into 1/2" pieces; toss in a large bowl with corned beef and 1/4 cup parsley. Moisten with cooking liquid if mixture is dry; season with salt and pepper.
Heat olive oil in a large nonstick skillet over medium heat. Add half of the corned beef mixture (or what will fit in the pan). Cook undisturbed, pressing down with a spatula, until underside is brown and crisp about 8 to 10 minutes. Carefully flip over the hash and cook the second side until brown and crisp another 8 to 10 minutes.
Transfer hash to a rimmed baking sheet (it may break up a little), tent with foil, and keep warm in oven until ready to serve.
Repeat with remaining olive oil and corned beef mixture.
For Poached Eggs:
Fill a sauce pan large enough to hold 4 eggs with 2" of water. Bring to a boil. Reduce heat to a gentle simmer and add vinegar. About 5 minutes before hash is cooked, crack an egg into a small bowl and gently slide egg into water. Repeat with remaining eggs, waiting until whites are opaque before adding the next (about 30 seconds apart). Poach until whites are set and yolks are still runny, about 3 minutes. Using a slotted spoon, transfer eggs as they are done to paper towels.
Serve eggs over hash, seasoned with salt and pepper and topped with chives and more parsley.
Notes
* This recipe works best if you prepare it over two days – make the corned beef on the first day and hash and eggs the following day. * Corned beef and vegetables can be cooked 2 days ahead; keep chilled until ready to use to make the hash.