To achieve a custard-like filling in Quiche Lorraine, which ingredient must be carefully blended with the eggs?

To achieve a custard-like filling in Quiche Lorraine, cream is the essential ingredient that must be carefully blended with the eggs. When making quiche, the combination of eggs and cream creates a rich, smooth texture that sets properly during baking, resulting in a delicate custard. The high-fat content of the cream enhances the overall richness of the filling, contributing to both flavor and creaminess.

In this context, sugar would not be suitable because it alters the flavor profile and is typically not used in savory dishes like quiche. Butter, while it can add flavor and richness, is generally not incorporated directly into the custard mixture and doesn’t contribute to the desired texture in the same way cream does. Flour could be used as a thickening agent in different recipes, but it is not standard in traditional quiche preparations, where the focus is on achieving a velvety custard consistency rather than a bready or dense filling.