Chef Mark Gordon, late of Coos Bay and Mo-dena, has fine-tuned his adventurous menu at Ambrosia, a handsome east Denver bistro featuring a lovely patio. But he has made no changes in his matchless rendition of osso buco, the classic Italian dish of sautéed veal shanks, veal stock, white wine, a touch of tomato, vegetables and herbs. Simmered for five hours, Gordon's masterpiece is fragrant with mingled scents of red pepper and orange zest, and it all but falls from the bone at the touch of a fork. To find a better version, you'll have to go to Italy.