Onion soup with hemp croutons
Onion soup with hemp croutons: 40 minutes of caramelization, four onions, and croutons coated in hemp flour. Proportions for four servings and a vegan version.
Onion soup relies on one thing: patience. The onion must change color on its own, over low heat, for nearly forty minutes, and no shortcut can replace that. What can be changed without loss is the croutons. Cubes of bread coated in hemp flour acquire a nutty flavor that balances the sweetness of the caramelized onion and add protein and fiber, which are almost absent in the soup itself. Hemp flour is not ground grain, but the residue from seeds after oil extraction: in a measurement published in the journal Foods, it contained 31.62% protein and 43.76% fiber in dry mass. Below are the proportions for four servings, the order of operations, and the places where this soup most often comes out flat.
KEY INFORMATION
• Hemp flour (Capcanari et al., Foods, 2023): 31.62% protein and 43.76% fiber in dry mass, compared to 12.45% and 1.51% in wheat flour.
• Caramelizing onions takes 35-40 minutes on low heat and cannot be shortened.
• Croutons made with hemp flour are baked at 180°C for 10-12 minutes.
• Without cheese and without wine, this soup is vegan and alcohol-free.
What does hemp flour bring to croutons?
Croutons in onion soup primarily contribute to the texture, while hemp flour adds flavor and nutrition. In a measurement published in the journal Foods, the residue from hemp seeds contained 31.62% protein and 43.76% dietary fiber in dry mass, compared to 12.45% and 1.51% in the wheat flour studied in the same paper (Capcanari i in., 2023).
The difference arises from the production method. Hemp flour is not made from ground grain, but from the residue left after oil extraction from the seeds. The fat leaves with the oil, while the protein and fiber concentrate in the remainder. Therefore, hemp flours from different producers can vary: the more thoroughly defatted the residue, the higher the protein content. The numbers above come from a single sample of one residue, so read them as an order of magnitude.
We noticed in our own trials that hemp flour adheres to bread cubes without egg and without water: just drizzle them with oil and mix. Breadcrumbs in this role tend to fall off onto the baking sheet, while hemp flour stays on the bread and bakes together with it. A nutty aroma appears about halfway through baking, and that's a good time to check the oven.
Why does caramelizing onions need to last 40 minutes?
Because the dark color and sweetness of the onion develop through two slow processes at once: in the Maillard reactions between sugars and amino acids, and in the breakdown of the sugars themselves. Both processes are more complete the longer they occur at a moderate temperature. Turning up the heat does not shorten them; it only burns the onion on the outside before it has time to soften on the inside.
A practical marker is simple. After a quarter of an hour, the onion is golden, soft, and quite tasty, but the soup comes out flat and watery. Only after 35-40 minutes does the color turn to dark amber, the volume decreases by more than half, and a brown sediment appears at the bottom of the pot, which you dissolve with wine or broth. This sediment carries most of the flavor of the finished soup.
Incidentally, it is worth correcting the widespread belief that long cooking increases the quercetin content in onions. Heat treatment does not create this flavonoid; it only changes its form. In a study on roasting onion glycosides, quercetin at 180°C broke down to the aglycone quercetin, which remained stable with further heating (Rohn i in., 2007). Caramelizing on low heat involves different conditions than roasting, so do not directly transfer this work to the pot. The conclusion that can be transferred is this: quercetin from onions withstands heating but does not multiply from it.
What do you need for onion soup with hemp croutons?
Proportions for four servings. Caramelizing onions takes 35-40 minutes, cooking the soup another 15, and the croutons bake for 10-12 minutes simultaneously, so the whole process wraps up in an hour.
- 800 g of onions, about four large pieces
- 1 l of beef or vegetable broth
- 3 tablespoons of butter or coconut oil for caramelization
- 2 cloves of garlic
- 100 ml of dry white wine or a tablespoon of lemon juice with a tablespoon of apple cider vinegar
- a sprig of fresh thyme and a bay leaf
- a teaspoon of sugar
- salt and pepper to taste
- 4 grube kromki chleba, pszennego albo bezglutenowego
- 2 tablespoons of hemp flour and a tablespoon of oil for coating the croutons
- opcjonalnie: 60 g startego gruyère albo parmezanu do zapiekania
Two shopping notes. Keep hemp flour in a sealed container, in a cool and dark place, because in the measurement mentioned above, the cake had 8.19% fat, which determines how quickly the flour will go rancid. If you are making a gluten-free version, the label on the bread and flour packages is decisive: the EU Commission Implementing Regulation No. 828/2014 allows the use of the term "gluten-free" only when the gluten content is up to 20 mg per kilogram of the finished product. You can find more about substitutes and proportions in our guide on hemp flour in baking.
How to cook onion soup step by step?
Five tasks, one of which takes longer than all the others combined. Active work here is about twenty minutes, the rest is done by a low flame. Put the croutons in the oven when the onion starts to darken.
- Caramelize the onions. Slice them into thin half-moons, heat fat in a wide pot over low heat, add the onions, salt, and sugar. Stir every 3-4 minutes for 35-40 minutes until the color turns a dark amber.
- Prepare the hemp croutons. Cut the bread into 2 cm cubes, mix the hemp flour with oil and a pinch of salt, coat the cubes in this mixture and spread them on a baking sheet. Bake at 180°C for 10-12 minutes until crispy.
- Build the soup. Add garlic to the caramelized onions and sauté for a minute. Pour in wine or a mixture of juice with vinegar and reduce for two minutes, scraping the sediment from the bottom. Add hot broth, thyme, and bay leaf, and simmer for 15 minutes on low heat.
- Season. Remove the thyme and bay leaf. The soup should be deeply sweet with a distinct umami note. Season with salt and pepper, and if the flavor is flat, add a teaspoon of soy sauce.
- Serve with croutons. Pour the soup into bowls and top with hemp croutons. Optionally sprinkle with grated cheese and place under the grill for 2-3 minutes. Serve immediately while the croutons are crispy.
How to modify the recipe for diet and taste?
The base is resistant to modifications because the entire flavor comes from the onion, not the additives. For a vegan version, replace butter with oil or coconut oil, and beef broth with vegetable stock; substitute the cheese for baking with nutritional yeast, which provides a similar umami note. The croutons made with hemp flour are vegan by definition, as only oil is needed for coating.
The alcohol-free version is a tablespoon of lemon juice and a tablespoon of apple cider vinegar instead of wine. It’s about the acidity that cuts through the sweetness of the onion, not the alcohol itself, so the effect is similar. You can add a crushed garlic clove to the hemp flour and oil mixture, which will cook together with the bread at 180°C.
The biggest mistake with this soup is shortened caramelization, and the second is too thin broth, which dilutes everything the onion has managed to build. If you are looking for a quicker soup, but with a hemp accent, check out our recipe for tomato soup with hemp oil albo na broccoli cream soup with seeds.
Frequently Asked Questions
What does hemp flour add to onion soup croutons?
A nutty aftertaste that balances the sweetness of caramelized onions, along with protein and fiber. In a measurement from the journal Foods, the hemp seed cake had 31.62% protein and 43.76% fiber in dry mass, compared to 12.45% and 1.51% in wheat flour (Capcanari i in., 2023).
How long does it take to caramelize onions?
For 35 to 40 minutes on low heat. After a quarter of an hour, the onion is golden and soft, but the soup comes out flat. A dark amber color, a reduction in volume of more than half, and a brown sediment at the bottom of the pot only appear at the end of this time.
Are croutons made with hemp flour gluten-free?
Hemp flour itself does not contain gluten, as hemp is not a grain. The type of bread determines the croutons. For a gluten-free diet, use bread labeled "gluten-free," which according to Regulation (EU) No. 828/2014 means a content of up to 20 mg of gluten per kilogram of the product.
What can replace wine in onion soup?
A tablespoon of lemon juice and a tablespoon of apple cider vinegar. The wine serves as an acid that cuts through the sweetness of the onion and helps to lift the sediment from the bottom of the pot, so any other acid of similar strength will work similarly. The alcohol evaporates within the first two minutes anyway.
How to store hemp croutons?
In an airtight container at room temperature for up to two days. Do not put them in the fridge, as moisture will take away their crispiness. If they soften, place them in an oven preheated to 180°C for three minutes, and you will restore their texture without re-breading.
The u Bucha store does not carry hemp flour and bread. In the category food you will find hemp teas and sweets for dessert after this soup.
The article is informational and educational in nature and does not replace consultation with a doctor. If you are pregnant, breastfeeding, taking medications, or have chronic conditions, consult the use of supplements or herbs with a specialist.
Author: Michał Waluk · Opublikowano: 2026-06-02 · Aktualizacja: 2026-08-15
