Cooking School Day 15: Boil & Simmer

Cooking School Day 15: Boil & Simmer

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Emma Christensen
Oct 24, 2014
(Image credit: Leela Cyd)
(Image credit: The Kitchn)
  • Today's Topic: Boiling and simmering
  • The Goal: 20 lessons, 20 days to become a better cook at home
  • Enter to win The Kitchn Cookbook: Simply share and tag photos of your Kitchn Cooking School progress on Instagram and Twitter with #kitchnschool to enter for a chance to win. We're giving away one copy for every homework assignment during The Kitchn's Cooking School. See rules and regulations.
  • Enroll & see all the lessons so far: The Kitchn's Cooking School

Boiling and simmering are the next two basic skills we're adding to our home cooking repertoire. With these solidly under our belts, we can poach eggs, simmer stews, reduce sauces, make stock and all sorts of other useful (and tasty!) kitchen endeavors.

Do you know what makes a simmer different from a boil? Or why recipes always say to bring to a boil, then down to a simmer? Let's dive in!

Watch the Video

(Image credit: Faith Durand)

Day 15 Lesson: Simmer

What's happening when foods simmer? As you probably already know, simmering and boiling both involve liquids, usually a large amount of liquid like a pot of water to boil pasta or simmering a soup. Simmering is a way of gently cooking ingredients until they are tender, but it's also a way of getting flavors in a dish to melt. As a soup or a sauce simmers, herbs and spices infuse the liquid, vegetables absorb some of that seasoned liquid while also contributing some of their own flavors back — it's synergy! Since some of the liquid evaporates while simmering and boiling, flavors are also more concentrated and intense by the end of cooking.

Boiling vs. Simmering: Think this a spectrum. At one end, you have a "slow simmer" and on the other end you have a "full rolling boil." At a slow simmer, you'll see very little movement in the liquid; wisps of steam and a tiny bubble or two every so often, but that's it. Then you have a "simmer," where you'll see some gentle bubble activity. A "rapid simmer" is just below a full boil; you'll see a lot of activity in the liquid but the bubbles will still be pretty small. When liquids are at a full, rolling boil, you'll see big bubbles and lots of churning, frantic activity in the pot.

Why is it important? In other words, why not just crank the heat and let a soup boil? Good question! The temperature of the liquid is a factor (liquid at a full boil is several degrees hotter than liquid at a slow simmer), but it's mostly about the action of those bubbles. A rolling boil causes ingredients to bump around a lot, causing them to disintegrate and also making the outsides mushy before the insides are fully cooked. At a simmer, the food is jostled just enough to move it around the pan and mix all the flavors, but not so much that the ingredients are damaged.

Fresh Chicken Stock
(Image credit: Dana Velden)

How to boil and simmer: It's all about controlling the heat! Liquids over high heat will boil rapidly, while liquids over a lower heat will simmer. Stovetops can be touchy, though, so you may need adjust the heat a bit to keep the liquid where you want it. Keep an eye on it — don't totally turn your back on the pot until you're sure the simmering is holding steady.

Pro Tip!

There's a myth that if you add salt to almost-boiling water, it'll raise the temperature and make it come to a full, rolling boil. While it make look like that is happening since the water bubbles furiously when the salt is added, what's actually happening is that the salt helps form bubbles but doesn't actually raise the temperature by any noticeable amount. The furious bubbling is only a temporary occurrence, so know that you're salting water for flavor, not for temperature.

Bring to a boil, then reduce to a simmer: It seems counter-intuitive, doesn't it? Why do so many recipes have you bring foods all the way up to a boil and then reduce it back to a simmer? The biggest reason is time: it can take quite a while for food to come to a simmer over medium-low heat; it's faster to bring it to a boil, then cut the heat back. It's also easier to control the simmer when you do it this way.

What recipes mean by boil and simmer: When a recipe says "bring to a boil," it means a true, rolling boil. Whether your boiling eggs or about to simmer a soup, you should see big bubbles and lots of roiling action in the pot. A recipe that tells you to "let simmer," means you should see small bubbles merrily popping the surface, but less action and vigor than a true boil. Be aware when a recipe says to use a "slow simmer" or a "rapid simmer" and adjust the heat under the pot accordingly.

Simmering and Boiling Cheat Sheet

  • Slow Simmer: Low heat, very little activity in the pot. You'll see wisps of steam and a stray bubble or two, but that's it. Most often used for stocks and braises.
  • Simmer: Medium-low heat, gentle bubbling in the pot. Most often used for soups, sauces, and braises.
  • Rapid Simmer: Medium- to medium-high heat, more aggressive bubbling in the pot, but the bubbles should still be fairly small. Most often used for reducing sauces.
  • Boiling: High heat, lots of big bubbles over the whole surface of the liquid, roiling activity in the pot. Most often used for boiling pasta and blanching vegetables.

(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: Fill a pan with water and bring it to a boil over high heat. Once it's at a full, rolling boil, start cutting back the heat in increments. Wait a few minutes at each increment until the activity in the water changes. Watch how the water goes through each of the stages, from boiling to a rapid simmer, then to a simmer, and finally to a slow simmer. The goal is to train yourself to recognize each stage so you can apply it later when cooking.

(Image credit: Henry Chen)

Practice: Boil or poach an egg — or both! Boiling eggs requires you to bring the water to a full, rolling boil. Poaching an egg requires you to simmer. Here are step-by-step instructions for both:

(Image credit: Henry Chen)

Improve: Make a batch of homemade vegetable or chicken stock. Stocks are best if they're left at an extremely low simmer for several hours — the low temperature and small amount of movement in the pan help extract all the good flavors from the stock ingredients without making the stock overly cloudy. This is a longer project, so set some time aside this weekend if you don't have the extra hours today!

The Kitchn Cookbook & Boiling & Simmering

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

Today's tip: One of Faith's favorite sets of photos in The Kitchn Cookbook appears on page 110 and it shows the difference between a boil and a simmer in a pot of water!

5 Recipes to Practice Boiling & Simmering

  1. Miso Soup with Rice & Poached Egg
  2. Quick Turkey Meatballs Over Greens
  3. Sloppy Joe Sandwiches
  4. Ham Bone, Greens, and Bean Soup
  5. Quick Weeknight Pasta with Hearty Tomato Sauce

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!

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