Culinary Arts

Chef Thomas Keller’s Caramelized Fennel Recipe: How to Sous Vide Fennel

Written by MasterClass

Last updated: Oct 14, 2019 • 2 min read

“All cooking is about time and temperature. The great thing about sous vide cooking is precision.” — Chef Thomas Keller, of Napa Valley’s Yountville restaurants Bouchon, Ad Hoc, and The French Laundry, and New York’s Per Se.

Transform raw fennel, which tastes of anise, or licorice, into flavorful fronds akin to caramelized onions with the recipe below.



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What Is Sous Vide?

Sous vide—French for “under vacuum”—is a cooking method that involves removing all of the air from a plastic bag or pouch using a vacuum sealer machine. This is not a new technique. You have seen it in supermarkets for years, in the form of vacuum-packed coffee, deli meats, turkeys, and boil-in- a-bag vegetables. The use of sous vide in restaurants and home cooks is more recent.

How Does Sous Vide Cooking Work?

The term “sous vide cooking” is a misnomer because it refers more to cooking food in a hot water bath kept at a precise temperature by a piece of equipment known as an immersion circulator. The role of “sous vide” in “sous vide cooking” is important in that removing all the air from the bag allows the food to cook effectively in the water bath and ensures even cooking by keeping the bag fully submerged in the water.

For professional and home cooks, sous vide cooking can be a wonderful technique for preparing a variety of meats, poultry, fish, fruits, and vegetables. But don’t think of it as a shortcut. In fact, it calls for longer cooking times at lower temperatures. When executed properly, your food will have amplified flavors and succulent textures.

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Chef Thomas Keller Sous Vide

What Do You Need to Sous Vide at Home?

For certain preparations, you can achieve excellent results at home using nothing more than heat-tolerant plastic wrap, a digital thermometer, a pot of hot water, and a stove. You can even take some of the guesswork out of it by downloading The PolyScience Sous Vide Toolbox, an app for iOS devices that makes it easier to determine the proper cooking and reheating times for a number of foods.

How to Caramelize Fennel

Watch Chef Keller demonstrate his method for caramelizing fennel.

Chef Thomas Keller’s Caramelized Fennel Bulb Recipe


This fennel preparation serves as a standalone appetizer or the ideal side dish to Chef Keller’s crispy salt-baked branzino.

  • 1 large fennel bulb, approximately 300 grams after trimming
  • 30 grams extra virgin olive oil
  • 3 grams kosher salt
  • 1 clove garlic, peeled, root removed
  • 1 sprig thyme
  • Canola oil


  • Chamber vacuum sealer
  • Vacuum sealer bag
  • Single-use gloves
  • Immersion circulator
  • Plastic container for water bath
  • Aluminum foil
  • Mixing bowl
  • Ice bath
  • Cooling rack set over a sheet pan
  • Kitchen scissors
  • Nonstick sauté pan
  • Plating spoon
  • Plate lined with paper towels
  1. Prepare a water bath with an immersion circulator set to 85 oC.
  2. Trim the root end of the fennel bulb, then remove the stalks and the outer layers of the bulb. Cut the bulb into six 3⁄4-inch wedges. Place the pieces in a mixing bowl and toss them with olive oil and a pinch of salt. Transfer the contents into a vacuum sealer bag, arrange the wedges in a single layer, and add in the garlic and thyme. Vacuum seal the bag and place it into the water bath when it reaches 85oC. Cover the water bath with aluminum foil for heat retention and minimizing evaporation.
  3. Cook the fennel for 40 minutes or until tender.
  4. Immediately plunge the bag into an ice bath to chill completely. Open the bag and transfer the fennel onto a cooling rack set over a sheet pan to drain. Discard the thyme and garlic.
  5. Heat a nonstick sauté pan over medium-high heat. Pour enough canola oil to thinly coat the bottom of the pan. When the oil is shimmering, place the fennel wedges into the pan. Caramelize the fennel until golden brown, about 3 minutes. Flip the wedges to caramelize the opposite side, another 3 minutes. Transfer the fennel to a plate lined with paper towels to drain.

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