Ube is a yam, Dioscorea alata, grown across the Philippines for thousands of years. It isn't taro, and it isn't purple sweet potato, though both get sold under its name. The colour is its own: anthocyanins, the same family of pigments that colours blueberries.
In Filipino kitchens it's boiled, grated, and stirred with butter, milk and sugar into ube halaya, a thick jam that takes patience and a strong arm. It's eaten on its own, layered into halo-halo, and baked into almost everything.
Filipino-American bakers carried ube into bakeries across the US, and now it's everywhere. Real ube is harder to find than the colour suggests, and a lot of “ube” is sweet potato or dye. So we'll tell you what's in ours: premium ube powder. No colouring, no flavouring.
“a colour you can’t fake, if you start with the real thing.”
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.