Let's take a look at Hungarian cuisine. The foundation of Hungarian culture is a sedentary, agrarian population, ruled over for several centuries by the Romans, that was invaded by various groups of nomadic steppe dwellers, adopting the language and certain cultural traits of the Magyars. Could goulash be the best example of such a fusion? Goulash comes from the Hungarian "gulyásleves" which basically means "herder soup". I've read some romantic conjecture that the concept of goulash originated in the cooking techniques of the nomadic Magyars, who cooked meat stews in large pots not unlike the Mongolians. This is mixed with ingredients only achieved through agriculture - various vegetables, tubers, and grain-derived products such as wheat-based noodles or rice.
That comes pretty close, though it is, of course, heavily influenced by modern European ideas and practices. One article we fairly consistently find in nomadic high-status contexts are cauldrons. It is suggested that they were solely used for serving alcoholic drinks, but I find that hard to credit. Your typical early modern Mongolian tripod cooking dish can be put to a number of uses, and a good-quality metal cauldron could likewise be a multirole item.
A thing to remember is that nomadic cultures in a metal age context always depend on sedentary populations. Their way of life is founded as much on trade and specialisation as it is on animal husbandry. Thus, using agricultural products is not an exception, but would have been the rule, though obviously the products preferred would be relatively lightweight and durable (dried pulses, grains and cereal products, dried vegetables and fruit, spices and herbs, not fresh vegetables or fruit as the Hungarian herders use).
The Romans with their cereal-heavy, sophisticated vegetable cuisine have much to offer to a Nomadic neighbour or ruling caste. Obviously their seafood fashion does not transport well, but then, it did not do that OTL, either, away from the Mediterranean. Their way of treating meats will go down well with the Mongols, I guess.