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Cooking School Day 2: Onions & Garlic

updated Jun 5, 2019
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(Image credit: Emma Christensen)
(Image credit: The Kitchn)
  • Today’s Lesson: Onions & Garlic
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Onions and their plucky little cousins, garlic cloves, are so foundational to so much of our cooking that we’re spending a whole day talking about them. Pull your onion goggles out of the drawer and get ready to chop some bulbs — it’s about to get pungent up in here.

(Image credit: Emma Christensen)

Day 2 Lesson: Onions & Garlic

Why are onions and garlic special? Why spend a whole day on one vegetable when there are so many lovely, colorful veggies out there? It’s because onions really form the bedrock of our cooking. They are often the first thing that goes in the pan, and they are the flavor base for everything from chicken soup to a quick weeknight skillet pasta. Cooked onions give dishes a rich umami flavor and a subtle sweetness — you don’t always know onions are there once the dish has been spiced and sauced, but you’d definitely miss them. Garlic is also important to these base flavors, and since it shares so many similarities to onions, we talk about them at the same time.

Basic Onion Anatomy: An onion is a bulb that grows just beneath the surface of the soil. If you look at one, you’ll see a hard round button on the bottom, possibly with some scraggly roots still growing from it. On the other end, the onions tapers to a neat point — this is where the green sprout would grow up into the air. An onion is covered by a few papery layers that can range in color from deep golden to light yellow to purple. Beneath the papery layers are thicker, edible layers that are very watery and smell quite powerful.

(Image credit: Emma Christensen)

Basic Garlic Anatomy: Similar to onions, garlic are bulbs that grow just beneath the soil. They also have a scraggly root end and a tapered point. Unlike onions, garlic grows in separate cloves — the whole bulb (a.k.a. “head”) will be covered with a few thin papery layers, but beneath those are separate cloves in their own paper-like jackets.

How to Prepare Onions and Garlic for Cooking: The outer papery layers are inedible; what we want lies beneath! Use your fingers to peel away the thin, tough papery layers around the onion bulb or the head of garlic. They should peel away fairly easily. With onions, it’s helpful to cut the onion in half through from pole to pole, through the root, then peel away the outer layers.

With garlic, once you’ve peeled away the outer layers, you still need to remove the tough paper from around the individual clove. To do this, you can smash the clove beneath the flat of your chef’s knife (like this), squeeze it like a lemon wedge until the skin cracks (like this), or shake it in a jar (like this). Once peeled, dice, slice, or mince the onions or garlic as directed in the recipe. Don’t forget to trim away the tough root end.

Watch the video below for the most fun way to peel garlic!

Controlling the Bite: Raw onions and garlic are potent creatures. Sometimes that’s desirable, as in a fresh salad or a green pesto. But other times… not so much. We control the “bite” and overall flavor of onions and garlic in two ways: the size of the cut and the cooking time. Smaller bits of onion and garlic will melt into a dish, becoming a subtle presence that gently infuses the whole dish, while large slices will have a more dominant presence. Also, the longer you cook onions and garlic, the more their flavor goes from sharp and biting to sweet and unctuous. The transformation is really incredible — you’d hardly think they’re the same vegetable.

Pro Tip!

If the taste of raw onions is too potent or spicy for you in a raw dish like salsa or salads, temper the bite by submerging the cut onions in cold water or acid from the recipe (like the lime juice in salsa or the vinegar in salad dressing) for about 10 minutes before serving.

Onions & Garlic in a Recipe: Recipes will usually tell you how the onions and garlic should be prepped right in the ingredients list: “1 yellow onion, diced” or “3 cloves garlic, minced.” It’s assumed that you will peel the onions or garlic before chopping and that you will discard the tough root end.

(Image credit: Emma Christensen)
(Image credit: Henry Chen)

Every lesson has three homework options. Maybe you’ve already got one down, or you just have time for a quick study session. So pick one, and show us by tagging it with #kitchnschool on Instagram or Twitter.

(Image credit: Henry Chen)

Study: Watch these videos: How To Dice an Onion and 3 Best Ways to Mince Garlic

(Image credit: Henry Chen)

Practice: Thinly slice an onion, paying close attention to the root and stem ends. Use the results of your labor in one of the recipes below to make dinner tonight.

(Image credit: Henry Chen)

Improve: Caramelize a batch of onions and taste them every 5 minutes as they cook. Along with tasting, watch how their color changes and how the aroma goes from sharp to sweet. Use all five senses! You’ll see how the onions go from raw and crunchy all the way to caramelized.

→ Here’s what to do: How To Caramelize Onions

How To Caramelize Onions (Image credit: Emma Christensen)

The Kitchn Cookbook & Onions

The Cooking School was inspired by our new book, The Kitchn Cookbook and there’s plenty in the book to help your Cooking School experience.

Today’s tip: See page 213 for a recipe that really shows off caramelized onions — Risotto with Chanterelle Mushrooms, Caramelized Onions, and Parmesan Cheese.

5 Recipes to Practice Cooking with Onions & Garlic

The Kitchn’s Cooking School

The Kitchn’s Cooking School is 20 days, 20 lessons to become a better cook at home. Every day we’ll tackle an essential cooking topic and explain what you should know. Each lesson has three different homework options, so you can choose the one that teaches you what you need. Whether you want to refresh your skills or start from scratch, come to school with us!