Japanese black tea, made from cultivars like Yabukita, tends to be sweet but short on aroma compared with Indian or Chinese teas. Adding flavoring is something the tea world instinctively resists — why mask a tea that already has its own scent? So we borrowed a technique emerging in coffee instead: barrel aging. We visited distilleries and coopers across Japan and found a route to casks that leak slightly, unusable for long whisky maturation but perfect for our purpose. Soaked in water and filled with tea, they pass on notes of anise, oak, and something faintly spirituous that no fermentation could ever produce. We think of it as a tea that can sit between people who drink and people who don't.

The second is a black tea fermented with koji. Strictly speaking, what happens in black tea and oolong is oxidation, not fermentation — no microbes are involved. True microbial fermentation belongs to teas like pu-erh, or Japan's own goishicha and ishizuchi kurocha, which rely on whatever wild organisms happen to be present in that particular place. That makes them difficult to control. We use koji instead, managing temperature and moisture ourselves so the result stays consistent.

What comes out is a complexity ordinary black tea can't reach. With a light roast at the end, it turns unmistakably cacao-like — chocolate, from a tea leaf. And because the koji feeds on the tea's polyphenols, it hollows out the leaf and multiplies its surface area, so it extracts extraordinarily well. You can even drip it like coffee.