Powdered tea began in Song dynasty China, where leaves were ground and whisked in a bowl. Around 1191, a Japanese monk named Eisai brought the method home, and later wrote a book about tea as medicine: Kissa Yōjōki, “drinking tea for health.”
His tea wasn't bright green yet. That came later, in the hills around Uji, near Kyoto, where growers learned to shade the plants for the last weeks before harvest. Less sun keeps the leaves sweet, savoury and vivid. Then they're steamed, dried and ground between stones, slowly: a stone mill makes roughly 40 grams an hour.
White chocolate is the newcomer. Nestlé put one of the first bars on sale in Switzerland in 1936. It's cocoa butter, milk and sugar, without the dark cocoa solids, which is exactly why it works here: it softens matcha's bitterness and leaves the green.
“shaded for weeks, ground by stone, forty grams an hour.”
The filling is made the day before, the dough rests overnight, and every cookie is filled and closed by hand. Then it's baked the morning you pick it up. No preservatives, because it was never meant to sit on a shelf.