It is! The tea in the photo is a pressed cake of Wuyi white tea.

Wuyishan has a very long history of tea, and some of the first tea ever produced in the region was actually pressed cakes of "green" (minimally processed) tea - similar to both green tea and sheng pu'er today, but the specific (very early) style of tea is no longer produced. This cake tea is what was used for tea competitions at court in the Song Dynasty - as you mention! - and it was with this tea in mind that Jian Zhan tea bowls were made. Cakes were ground into "mo cha" (ground and powdered tea), then the tea was whisked to produce a very fine foam. The bright foam was a stark contrast to the darkness of the tea bowls. As traditions evolved and new dynasties rose and fell, Wuyishan eventually moved completely away from this old / original style of early tea, instead pioneering the world's first black tea and their famous "cliff tea" Wuyi oolong. Meanwhile, Buddhist missionaries had brought tea and "mocha" (matcha!) with them to Japan, where the whisked tea tradition continued on to what we see today.

Lin Xi was using a cake of the Li Family's Wuyi white tea in the photos you see above for a few different reasons. In part, this "new" (old? revival?) style of tea is closest to the sort of thing that would have been used in the Song. White tea made from the Bai Mu Dan cultivar also has the benefit of being covered with lots of fine downy trichomes - and these are critical in producing a fine foam. Many fine green teas also have beautiful amounts of down, but nowhere near the amounts you can get with a cultivar like Bai Mu Dan. The minimal processing on white tea also preserves these trichomes better than - for example - making oolong tea. The additional handling, processing, and roasting for oolong teas means that much of this downy material will be lost, even when you start with a particularly downy cultivar.

To whisk the tea, Li Xi first breaks off a small amount of tea from the white tea cake. Then, he heats the leaves for a short time on a little induction range - this is to remove moisture, and will make grinding easier and more even. He immediately grinds the leaves manually in a mortar and pestle, and then transfers this to a traditional stone mill that he commissioned with Li Xiangxi (very similar to mills used in Japan for matcha) as part of his research in Song tea + teaware. He grinds the tea in the stone mill, which produces a very, very fine powder.

To whisk the tea, you actually use a different technique than what you usually see in Japan. Instead of combining all of the tea and the water directly in the bowl and then whisking, Lin Xi starts with adding a very small amount of water to the powder, and whisks. Very gradually, he adds a little more water at a time. This builds up the foam slowly, as the whisking continues to whip air into the tea / water mixture. This slow process traps air between the buddy down of the tea (similar to the way the proteins in egg whites trap bubbles when whipped for a meringue). Finally, when all the water has been incorporated, the foam is very tall, fluffy, and nearly bright white. Drinking it - amazing!!!!

The whole process from breaking open a cake to sipping the tea happens one step right after the other, and takes about thirty or forty minutes. Worth it!