Custards are essentially eggs and dairy that set when gently heated—too hot and they curdle, too cool and they stay runny. Sous vide gives you a stable water bath that cooks jarred custards evenly, so you get a silky, spoonable set without bubbles or weeping. Use the lower end for crème brûlée–style wobble, and go a touch higher for firmer egg bites that hold their shape. This guide focuses on temperature, jar size, and the chill time that finishes the texture.