The three essential ingredients in this soup--garlic, bread, and water--all need to be of good quality. Do not be tempted into thinking that stock is an improvement since it masks the other flavors. Beyond that, though, you can improvise around the local variations in ingredients: lard is used rather than olive oil in Zamora, for example, and pepper seeds and chopped tomatoes are added in León. You can also sauté the garlic first. Usually the bread is broken into small pieces so it swells into sops, but I like this fried-bread version given to me by Vale Riana, who was born in the Burgos countryside but cooked for a Madrid family for thirty years. Garlic soup was often eaten early on winter morning before going out into the bitter cold, and I really enjoy it that way.