Going back 1,400 years would lead us to the Sui and Tang Dynasties. For convenience, I will talk briefly on the Tang Dynasty as A) I know more about it B) It is regarded as one of the high points in dynastic China, most notably culturally.

I believe one thing that would not seem foreign would be tea, even including the concept of tea bags. At the time, tea was promoted for its medicinal properties. As the Tang Dynasty is seen as a cultural apex for some types of art, tea can even be found in poems and other forms of the written word.

However, foodstuff would seem more alien. In particular, modern Asia's consumption and use of oil. Also, rice was still difficult to cultivate at the time, so the majority of the population survived on millet. One can easily find millet today in Asia countries. I am aware that some aboriginal tribes in Taiwan, for example, still maintain millet is a stable in their diets.

Edit: to add while on my commute. Taking the above into consideration, it is important to note how the food was prepared. This is where oil creates division. In the Tang Dynasty we see a lot of boiling and water-based porridges. However, stir frying and deep frying are now pronounced.

To end, seasoning (marinating, if you will) was also important for individuals in the Tang Dynasty. Items like cinnamon, salt (preservation), ginger, and pepper were often included in recipes.

The center of Chinese civilization 1400 years ago was still strongly centered around the yellow river, and the cuisine was strongly influenced by what was and what still is grown in the yellow river valley. Namely, people subsisted off the small grains and other grain crops: wheat, barley, millet (not sure about sorghum or oats). The south of China was no where near as settled as it became during the Song dynasty. The paddy style agriculture that is now ubiquitous from the Changjiang downwards was really just beginning during the Tang, and rice played a small role of say, your average person in or near Kaifeng, Luoyang, or Xian.

As for cuisine in its overall general totality: The cuisine would be quite different for your "average" southern rice dependent Chinese, but very recognizable for a Northerner and especially for someone from Henan, Xi'an, Shanxi etc. There is absolutely no reason why staples like Millet Porridge, Noodles (Hui mian or Liangpi), or dumplings made from vegetables or beef, lamb, or goat or simply rolls (mantou), wouldn't be steamed or boiled from homegrown materials as they are today.

One overarching thing that would come if an average Chinese person, or really any person who went back to medieval Europe or Asia. Staples such as potatoes, tomatoes, and chile peppers (which play a prominent role in their cuisine today) would be nonexistent due to only being in the Americas before the Colombian Exchange. And, while tropical spices like black pepper and cumin would be available in China from places such as Indonesia or India, the extraordinary costs in their transportation would strongly limit consumption of such things to the point that you would have to be very wealthy to regularly consume these spices. Local spices would, theoretically speaking, have been used prevalently.