Rogue was about Westchester hash. I'll offer some leads. Others follow, please. None of these are recent, so caveat eater:
Port Chester: Crossroads Café (141 Willett Ave 934-5065) sweet potato and sausage hash.
yorktown: Grandma's Country Pie and diner 3525 Route 202 739-7770 corned beef hash near the Bear Mountain Parkway and Taconic
City Limits Diner in white plains, which I otherwise dislike, I THINK might make pretty ok corned beef hash
and, just over border in dutchess county
Pawling: fine food cafe (10 Charles Colman Blvd; 845-855-3875 corned beef hash served in a frying pan with chunks of corn beef.