Everyone, even the most hard-core, everything-from-scratch purist, will admit that the best corned beef hash in the world is the stuff that comes straight out of the can — mushy, smelling like cat food and with that slick white cap of fat on top that would keep the hash fresh even if the can remained unopened for 10,000 years. But the second-best hash (at least in this city) is at Mona's, where an order brings sliced corned beef brisket, cut the size of bathroom tiles and given a fast sear in the pan, along with deep-fried potatoes, crisp on the surface and soft within like perfect pommes frites, and big chunks of green bell pepper and sautéed onions. True, it's dangerous to screw with the vital corned beef/potato/fat ratio. And for a moment, this plate will horrify anyone who grew up with the canned stuff and, even today, loves it all out of proportion. But be brave. For scratch hash, Mona's beats every other breakfast bar in the city.