How to Make Vegetable Soup with Your Fall Harvest: A Simple Formula

From Fall Harvest to Soup Pot

When the temperatures finally break and the brisk autumn air returns, the garden tells you it’s time to make soup. The cool season vegetables are begging to be roasted, sautéed and puréed into autumnal goodness. Sweet potatoes, carrots, winter squash, onions, cauliflower and other fall veggies can become a warm satisfying soup without following a completely different recipe every time.

Once you understand my basic formula for how to make vegetable soup, you can use what you grow, what you find at the farmer’s market, or simply what needs to be used in the refrigerator and freezer.

In this guide, I’ll show you my basic fall harvest soup method and use Sweet Potato, Carrot and Thyme Soup as an example.

The Fall Harvest Soup Formula

Vegetables + Aromatics + Herbs + Broth + Blend + Finish = Soup

The exact amount of broth will depend on the vegetables you’re using and how thick you like your soup. Start conservatively. You can always add more broth.

Step 1: Choose Your Fall Vegetables

Start with 4-6 cups of chopped vegetables.

Great choices include:

• Sweet potatoes
• Carrots
• Butternut squash
• Pumpkin
• Acorn or other winter squash
• Parsnips
• Potatoes
• Cauliflower
• Turnips
• Rutabaga

Step 2: Build Your Flavor Base

Begin by cooking aromatics in olive oil or butter.

A classic mirepoix is a combination of onion, carrot and celery cooked gently in fat to create the flavor foundation for soups and sauces.

But mirepoix isn’t your only option.

Try:

• Onion
• Onion + garlic
• Shallot + garlic
• Leeks
• Onion + celery
• Traditional onion + carrot + celery

Should I Sauté or Roast My Vegetables?

These are both good ways to build flavor.

Sauté

Sauté the aromatics and vegetables in your soup pot until they begin to soften and develop some color. I love my cast iron dutch oven from Le Creuset! It is a workhorse in my kitchen.

This is the easiest method for a one-pot soup. Chop and drop into the pot. The secret is to let them sauté long enough that they start to caramelize and leave some browning bits in the bottom of the pot.

Roast

Roast vegetables such as squash, carrots, sweet potatoes and onions until tender and caramelized, then transfer them to the soup pot.

Roasting takes a little longer but creates deeper, sweeter flavor. In this method, the vegetables are caramelized in the oven, not the pot.

Step 3: Add Fresh Herbs

Cool season vegetables pair especially well with herbs from the kitchen garden. Try adding:

• Thyme
• Sage
• Rosemary
• Parsley
• Cilantro
• Chives

Add sturdy or woody herbs like mature thyme, rosemary and sage during the cooking process. Save the more delicate herbs like parsley, cilantro and chives for finishing.

For the sample soup I’m making, fresh thyme balances the natural sweetness of the carrots and sweet potatoes.

Read my post How to Grow, Harvest and Cook with Fresh Thyme for more insight on this essential kitchen herb.

Step 4: Deglaze the Pot and Save the Fond

Once your vegetables have developed some color, add a splash of broth.

Use a wooden spoon to scrape the browned bits from the bottom of the pot.

Those browned bits are called fond, and they’re concentrated flavor. When I was teaching my youngest daughter how to cook, I told her this was the “gold” in the bottom of the pot or skillet. Never let it go to waste!

Work it back into the soup rather than leaving it behind.

Then add enough broth to mostly cover the vegetables.

Step 5: Simmer Until Completely Tender

Bring the soup to a gentle boil, reduce the heat and simmer until the vegetables are very tender.

Depending on the vegetables and the size of your pieces, this will generally take about 15–25 minutes.

If you’re planning to purée the soup, the vegetables should be soft enough to easily mash with a fork.

Step 6: Blend and Adjust the Consistency

I prefer to use an immersion blender directly in the pot. If you don’t have one, carefully ladle small amounts into a blender or food processor to purée. Hot steam can build up and can make a disastrous mess if you aren’t careful-so take your time!

You can make your soup:

• Silky smooth
• Mostly smooth with a little texture
• Partially blended and rustic

Let the vegetables thicken the soup

For puréed harvest soups, you usually don’t need flour, cornstarch or another thickener.

Sweet potatoes, winter squash, pumpkin, potatoes, carrots and other vegetables naturally give the soup body once they’re blended.

If the soup is too thick: Add broth a little at a time.

If the soup is too thin: Simmer uncovered for several minutes to reduce it.

Step 7: Taste Before You Finish

Before adding cream or toppings, taste your soup and ask yourself:

• Does it need salt?
• Does it need more pepper?
• Would a little acidity brighten it?
• Does it need more broth?
• Is there enough herb flavor?

If the soup tastes a little flat, try a small squeeze of lemon juice or a splash of apple cider vinegar before automatically adding more salt.

Step 8: Finish Your Soup

Finish the soup with some unique toppings. This is what allows one basic soup formula to go in completely different directions.

Simple Soup Finishes

• Extra-virgin olive oil
• Heavy cream or half-and-half
• Butter
• Freshly cracked pepper
• Fresh herbs
• Parmesan
• Homemade croutons
• Toasted pumpkin seeds
• Sour cream
• Plain Greek yogurt
• Squeeze of lemon

Gourmet Soup Finishes

• Crispy sage leaves
• Brown butter
• Chili-infused olive oil
• Maple-toasted pepitas
• Candied pecans
• Toasted hazelnuts
• Crème fraîche
• Herbed goat cheese
• Parmesan crisps
• Garlic-herb croutons
• Crispy shallots
• Roasted garlic oil
• Thin apple or pear matchsticks
• Herb oil
• Crispy prosciutto
• Microgreens
• Golden raisins
• Dried cranberries

An Easy Finishing Formula

For a special bowl, choose:

Something creamy + something crunchy + something fresh or flavorful

For example:

Cream + pepitas + fresh thyme

Crème fraîche + crispy sage + brown butter

Olive oil + croutons + parsley

You don’t need all three every time. A simple drizzle of good quality olive oil and freshly cracked pepper may be all a weeknight soup needs.

To show you how to make vegetable soup with my formula, I made a Sweet Potato, Carrot & Thyme soup.

Sweet Potato, Carrot & Thyme Soup

Let’s break down the process with this sample harvest soup together.

Ingredients:

• Olive oil and/or butter
• Onion
• Sweet potatoes
• Carrots
• Fresh thyme
• Chicken or vegetable broth
• Salt
• Freshly ground pepper

Optional:

• Heavy Cream or crème fraîche
• Olive oil
• Pepitas
• Fresh thyme for garnish
• Seasoned croutons

Sauté Method:

1. Heat olive oil and/or butter in a soup pot.
2. Sauté the onion until softened and lightly caramelized.
3. Add chopped sweet potatoes and carrots.
4. Continue cooking until the vegetables begin to develop a little color.
5. Add fresh thyme.
6. Pour in a small amount of broth and scrape the fond from the bottom of the pot.
7. Add enough additional broth to mostly cover the vegetables.
8. Bring to a gentle boil, reduce the heat and simmer until the vegetables are completely tender.
9. Remove thyme sprigs.
10. Blend with an immersion blender until smooth.
11. Add more broth if needed to reach your preferred consistency.
12. Taste and adjust the salt and pepper.
13. Add a splash of cream if desired.
14. Finish and serve.

Oven Roast Method:

1. Heat oven to 425°F.
2. Toss chopped vegetables with olive oil and seasonings.
3. Layer vegetables evenly on sheet pan and roast for 25-30 minutes.
4. Heat olive oil and/or butter in dutch oven on stove top.
5. Add roasted sweet potatoes, carrots and onions.
6. Add fresh thyme.
7. Pour in a small amount of broth and scrape the fond from the bottom of the pot.
8. Add enough additional broth to mostly cover the vegetables.
9. Bring to a gentle boil, reduce the heat and simmer until the vegetables are completely tender.
10. Remove thyme stems.
11. Blend with an immersion blender until smooth.
12. Add more broth if needed to reach your preferred consistency.
13. Taste and adjust the salt and pepper.
14. Add a splash of cream if desired.
15. Finish and serve.

Everyday Finish

Olive oil + toasted pepitas + fresh thyme

A Little Fancier

Cream swirl + toasted pepitas + fresh thyme

Dinner Party Finish

Crème fraîche + crispy sage + maple-toasted pepitas

Create Your Own Fall Harvest Soup

Once you understand the method, you can stop thinking in terms of individual recipes.

1. Choose the harvest: Pick 1-3 fall vegetables totaling roughly 4-6 cups.
2. Build a flavor base: Choose onion, garlic, shallot, leek or mirepoix.
3. Choose an herb: Sage, thyme, and rosemary are perfect for fall vegetables.
4. Develop some color: Sauté or roast your vegetables to build flavor.
5. Add broth and simmer: Use chicken or vegetable broth and cook until everything is tender.
6. Blend: Make it silky smooth, slightly textured or rustic.
7. Taste: Adjust salt, pepper, acidity and consistency.
8. Make it Yours: Choose a simple finish for dinner tonight or dress it up for company.

Five Fall Harvest Combinations to Try

Butternut Squash + Apple + Sage

Finish with crème fraîche and crispy sage.

Pumpkin + Carrot + Rosemary

Finish with toasted pepitas and olive oil.

Cauliflower + Potato + Garlic

Finish with Parmesan, chives and homemade croutons.

Carrot + Parsnip + Thyme

Finish with Greek yogurt and toasted walnuts.

Sweet Potato + Butternut Squash + Sage

Finish with brown butter and maple-toasted pepitas.

From the Garden to the Soup Pot

Learning a basic soup formula means you don’t need a new recipe every time you bring vegetables in from the garden.

Choose your harvest, build some flavor, add herbs and broth, simmer until tender, blend and taste. Then decide whether tonight’s bowl needs nothing more than a drizzle of olive oil or if it deserves the cream swirl, crispy sage and toasted pepitas.

Once you know the method, a basket of mismatched fall vegetables starts looking a lot more like dinner.

Looking for more soup ideas? Read 10 Soup Recipes for Fall, perfect for autumn.