For our challah, we borrowed the water roux (also called tangzhong) technique that’s used to make tender, fluffy Japanese milk bread. A water roux is a mixture of water and starch cooked to a gel-like paste. It’s a way to increase the hydration level in a bread dough but keep the mixture workable (instead of turning it wet) while also extending the shelf-life of the baked loaf. In our challah, the water roux also helped produce a better-structured crumb, with the light, feathery quality characteristic of the bread. Oil is the fat of choice in traditional challah. For more complex, nuanced flavor, we chose extra-virgin olive oil over a flavorless neutral oil. And to complement the fruity, peppery notes of olive oil, we mix golden raisins plumped in orange juice into the dough at the end of kneading. Though we love the look of challah formed into an intricate six-strand braid or an impressively mounded crown, for ease, we make two simple braids and bake them in loaf pans. Well wrapped, the loaves will keep at room temperature for two or three days. For longer storage, wrap in foil and freeze for up to a month. To refresh, thaw the still-wrapped loaf at room temperature (about 30 minutes), then completely unwrap, place on a baking sheet and warm in a 300°F oven for about 15 minutes.