The Harrison 355 Greenwich St.  New York, NY  10013-2844  Phone: (212) 274-9310 The Atmosphere The Harrison brims with a warm, festive energy that makes it easy to forget that the restaurant sits only blocks from the devastation of Ground Zero. The interior has the homey, agrarian appeal of a Midwestern kitchen, with aged-looking wood floors, wrought-iron chandeliers and a squash-topped hutch in a corner.  The Food  Full-flavored seasonal comfort foods, some prepared in an Italian vein, represent the best of the New American menu. Manageable portions and an abundance of very good side dishes invite sharing--an ideal spread might include perfectly firm cavatelli with veal cheeks; lightly sweet, marble-sized Brussels sprouts with candied pecans; a rich, texturally varied pumpkin risotto; a thick, juicy grilled pork chop; sautéed day-boat cod over mashed potatoes and a meaty shell steak sealed in a crackling black crust. Desserts--apple cobbler, chocolate beignets--are a minor disappointment.