The Foolproof Formula For Making Soup With Whatever's in Your Fridge

Sometimes you have the perfect recipe in mind with all the ingredients ready to go. Other times, you find yourself staring into the fridge, racking your brain over how to turn what's inside into dinner.

In a situation like this, a trip to the grocery store or a scroll through Pinterest for some inspo might feel like the best answer, but the truth is you probably already have everything you need to make a delicious and healthy soup from scratch. While many classic soups like broccoli cheddar or French onion have a set list of ingredients, you don't actually need to have a recipe to work from or adhere to any precise measurements. All you need to do is follow this formula and you can easily make soup with whatever's in your fridge.

How to Make Homemade Soup

Soup consists of four key elements: the base, aromatics, liquid, and mix-ins. As long as you have ingredients that fit into each of these categories, you can make a soup. It's best to add each component in stages rather than dumping them in all at once because it will ensure none of the ingredients get overcooked.

Base

The base of a soup is formed by a combination of fat, vegetables, and (optionally) starch. These ingredients create depth of flavor, forming a foundation of sweet and savory that other ingredients can easily build upon to round out the soup's overall flavor.

To create the base, you'll first need to add the fat, which can be oil, butter, or even bacon. Next, add the vegetables, typically onion, celery, and carrots, or what's called a "mirepoix." Some also include peppers and tomatoes, but you can essentially use any vegetable that caramelizes well and has a relatively neutral flavor.

The last component of the base is the starch, but that's only added if you want a thicker, heartier soup. The starch can be flour, potatoes, barley, or rice. While pasta is technically a starch too, it should be added later into the process because it cooks much faster.

Aromatics

Aromatics are considered to be any ingredient that has a strong flavor and aroma, typically garlic, herbs, spices, and seasoning blends.

The aromatics you choose establish the main flavor of the soup — whether you want it to be spicy, herbaceous, earthy. Soups that are popular in the fall, for example, often use warm spices like nutmeg, cloves, and cardamom to give it that cozy, seasonal taste. If you're aiming for a more Italian-inspired flavor, you might use herbs like basil, oregano, and parsley.

Some choose to add the aromatics towards the end of the cooking process, however when it comes to soup, adding them fairly early actually allows the flavors to fully develop and meld with the other ingredients in the soup.

Liquid

A soup really starts to come together once you add the liquid, which can be broth, stock, or water, as well as milk or cream if desired.

Use water as the liquid in your soup if you want a lighter broth that lets the other ingredients shine, and use broth or stock if you want a richer broth with more layers of flavor. Broth and stock are similar, but stock is simmered longer, made with bones rather than meat, and is generally left unseasoned. It has a darker color, thicker consistency, and gelatinizes when cold. Broth is simmered for less time, uses the meat rather than the bones, and contains more seasoning, so if you want more control over the seasoning and salt levels in your soup, choose broth over stock.

You can also add cream or milk at this stage to make your soup creamier, or blend it all up for a smoother consistency. After you customize it to your liking, taste test your soup and add salt if needed.

Mix-Ins

The mix-ins add substance and texture to a soup. These include any proteins, pasta noodles, and vegetables of your choosing.

You can really get creative with the mix-ins for a soup and use anything in your fridge. If you want to get rid of a leftover rotisserie chicken or find a way to use up the rest of your zucchini before it goes soft, this is the perfect opportunity to do so. Just make sure to chop everything consistently so it cooks evenly.

Once all the mix-ins are in, crank up the heat of your stove and once the liquid reaches a boil, bring down the temperature to a simmer and cover it with a lid. You'll know it's done cooking when the mix-ins are tender but not mushy.

How to Make Soup Thicker

If you've already added a starch to the base and realize your soup didn't turn out as thick as you hoped, the good news is there's an easy solution: All you have to do is take any refined starch — flour, cornstarch, or even instant mashed potatoes — and turn it into a slurry.

To do this, add some of your soup broth into a small bowl, and whisk in the starch, gradually adding more of each as needed until it forms a thin pourable liquid you can mix into your soup.

You may be tempted to just dump the starch into the pot, but this will create lumps of flour in your soup. Continue adding more slurry until you reach your desired consistency, but keep in mind, the more you add, the cloudier your soup will become. If you want to keep any cloudiness to a minimum, simply let the soup simmer longer so some of the liquid evaporates and naturally thickens it.

How to Make Soup Clear

Deciding early on in the cooking process whether you want your soup to be clear will save you from troubleshooting later. The key is to avoid adding any starches to the base and to strain out the aromatics and base ingredients once they've cooked in the broth.

While taking these steps is the best case scenario, it isn't impossible to turn an already cloudy soup to a clear one. To do so, you'll need egg whites: After separating them from the yolks, whisk the egg whites until frothy and pour into the soup while simmering. They'll initially sink to the bottom before floating to the top to form what's called a "raft."

As the egg whites cook, they'll also trap any tiny particles causing the soup to look cloudy, and then you'll be able to remove the raft all in one chunk. You can then strain the soup to clarify it even further.

Is it Safe to Can Homemade Soup?

Soup can be a convenient meal to pull together once you know the formula, but it'll spoil after three to four days. If you've made extra and want to keep enjoying it past this point, the best course of action is to freeze it, which would extend its lifespan to two to three months.

Canning is also an option, however it's not always the safest choice. According to the USDA, only soups without any dairy, pasta, rice, flour, or thickener can be safely canned, as these ingredients can prevent heat from properly penetrating the soup, risking spoilage and bacterial growth. Even if you made a soup that was free of these ingredients, it still requires an actual pressure canner — rather than a boiling water bath — unless it contains a lot of high-acid ingredients like tomatoes or lemon juice, which are less prone to bacterial growth.

If you're unsure whether your soup is safe for canning, freezing is a safer bet. Remember, you can always make another batch with a fresh set of ingredients using the same simple soup formula.

Kalea Martín writes primarily about food and cooking for PS, but as a former figure skater and hockey player, she covers fitness, too. Prior to becoming a lifestyle writer, Kalea covered hotels, restaurants, and travel for Luxos Magazine in Milan and worked in marketing at HarperCollins Publishers.