Sautéed Shallots Are A Key Ingredient In Julia Child's Spinach Soufflé
Esteemed cook and television personality Julia Child was enormously influential in popularizing French cooking in America in the 1900s. Child co-authored two volumes of the seminal "Mastering the Art of French Cooking," which, if you don't already have copies in your kitchen, we'll wait while you order some. Because of her highly-developed abilities as a cook and reliability as a recipe source, it's always advisable to make Child's version of any dish first and apply your own modifications later. So, when she suggests in Volume 1 to include shallots in a spinach soufflé (more accurately, Soufflé aux Épinards) in lieu of onions, do it now and thank her later.
Why should you cook with shallots? Well, there's both a long answer and a short one. First, it gives you an opportunity to stand over a pan and smell thinly sliced shallots sautéing in butter, which is one of life's most rare and exalted pleasures (if you know, you know). Beyond that, shallots' taste is more elevated than their bigger brethren: More complex, more delicate, and more je ne sais quois. We'll get to the long answer in a minute.
Of shallots and soufflés
As for the longer answer about why you should use shallots when making a soufflé, it has to do with the structure of their cellular walls. Shallots break down more readily than their allium cousins, becoming almost liquified after a while. This accomplishes two things: One, caramelization happens more quickly (it's no surprise that sweet, crisp-fried shallots are universally loved), and two, shallots' melty nature is ideal when making smooth sauces and light, airy things like a soufflé. Bon appétit!
In Child's recipe for spinach soufflé, you begin sautéing shallots right after preparing the mold with butter and cheese and blanching the spinach. This is a fairly quick affair because the chopped spinach is added almost immediately in order to evaporate most of its water (which it has plenty of). After that, it's a pretty traditional French soufflé: A roux is made with more butter and flour, into which are whisked egg yolks, hot milk, and the spinach mixture. The secret of a fluffy soufflé lies in the beaten egg whites, which are then folded in. More cheese is added, naturally, and then into the preheated oven it goes.