NYT Cooking: Dongbei cai is the food of Northeast China. Weiliang Chen, the chef at Northeast Taste Chinese Food, the biggest of the Dongbei restaurants in Queens, makes an elegant, tender version of a popular Dongbei stir-fry of lamb with dried chilies, made fragrant and crunchy with cumin seeds — a legacy of the nomadic Mongols who long ruled Central Asia, carrying spices on horseback along with their arrows. Lamb is considered a Northern taste and excessively “strong” by many Chinese coo…