Egg drop soup, or dan hua tang—literally “egg flower soup”—is a Chinese home cooking staple. It’s simple, quick, and comforting, especially as the weather turns colder. The “flower” refers to the soup’s characteristic soft, wispy ribbons of egg, formed by slowly pouring in beaten eggs near the end of the cooking process. They add color and texture to the simple chicken broth base, slightly thickened with cornstarch and made fragrant with ginger, scallions, and white pepper. Egg drop soup is very adaptable, so feel free to throw in other ingredients, such as quick-cooking vegetables or your protein of choice. In this version, diced tomatoes add some welcome brightness. This recipe calls for making your own basic chicken stock for the base, which is easy if you plan ahead: When cooking other dishes that require cutting chicken meat off the bone, leave a bit of meat on the bones and save …