Jacques Pépin's Favorite Shortcut To Thicken Soups

Few people can bridge classic French cuisine to American cuisine. Jacques Pépin has done that for decades, per Culinary Schools. What makes his cooking so unique is that the bridge he built doesn't just reach fancy restaurant kitchens. His recipes and innovative techniques land firmly, and comfortably, in home kitchens.

Traditionally, many soups are thickened toward the beginning of the recipe. According to Masterclass, a roux is a common method for adding body to many soups. For a roux, wheat flour is cooked in an equal amount of oil or butter. That cooking eliminates a raw flour flavor but lets the starch thicken the soup. It's a basic technique in many cuisines and was certainly something Pépin started doing as an apprentice in French kitchens decades ago.

As simple as a roux is to make, it can be difficult to get the roux-to-liquid ratio correct. In the end, your soup can be too thick, which is easy enough to dilute. But if your end result is too thin, what are the solutions?

Aside from using a roux — the classic method of bringing body and thickness to soup — there are many alternatives. Using a blender to puree vegetables into a soup is great for a perfectly smooth, velvety butternut squash soup recipe. Or you can use a blender to puree just some of the ingredients in your soup, according to the BBC, and leave another portion whole for a chunkier result.

They also prescribe adding some dairy in the form of cream or yogurt. Adding a cornstarch slurry is a good way to thicken a soup at the end of cooking. Bread is a viable secret ingredient to thicken soup. Lentils or rice can be added to absorb some of the extra liquid, but those additions might need to be pureed after they finish cooking. For thickening gravy — though this is translatable to soup – Masterclass suggests something similar to a roux, called beurre manié. This "kneaded butter" is softened butter and flour that's been mixed into a paste that can be whisked into the soup at the end of cooking.

Those are all great options. But, what if you don't eat dairy or can't have bread? Or maybe you don't have a blender? Leave it to Jacques Pépin to find a better way.

Starting at the 4:12 mark of this video from his show "More Fast Food My Way," Pépin makes his version of cream of leek and mushroom soup — and his thickening method is a revelation. Instead of using a traditional roux, he adds instant mashed potato flakes. The result is fast, rich, and easy to adjust.

Pépin sweats thinly sliced leeks (pay attention to his simple way to trim and wash leeks) and mushrooms for a few minutes, covers with broth, boils for a few minutes, adds the instant potatoes, brings to a simmer, and serves. Adding some dairy is up to you. Either way, you have a hearty dinner within 20 minutes. 

Though this method would obviously also work well in potato-centric soups and stews, potato's mild flavor plays well with so many others that this tip can work with most any recipe that needs some thickening. According to Oregon State, instant potatoes are a good substitute for cornstarch. As a plus, there's no need to make a slurry — just add the flakes, stir, bring to a simmer, and add more if needed. They recommend using one tablespoon of potato flakes per cup of liquid.