Onion soup with hemp croutons

Classic onion soup requires one thing above all: patience when caramelizing the onions. You can't rush this process without sacrificing flavor. However, it can be enhanced – croutons coated in hemp flour instead of regular bread bring something that the classic version lacks: plant protein, fiber, and a nutty flavor that perfectly balances the sweetness of the caramelized onions. Hemp flour is naturally gluten-free, contains about 30% protein, and gives the croutons a distinctly different character. Below is the full recipe with nutritional values and tips for caramelization.

KEY INFORMATION
• Hemp flour contains about 30% protein and 28% fiber – significantly more than wheat flour (10% protein, 3% fiber) (Mattila et al., 2018).
• Hemp flour is naturally gluten-free and has a glycemic index below 35 (Siano et al., 2019).
• Caramelizing onions requires a minimum of 35–40 minutes over low heat – you can't shorten this without losing flavor.
• 100 g of hemp flour provides about 330 kcal, 30 g of protein, 11 g of fat, and 28 g of fiber (USDA FoodData Central, 2023).

What does hemp flour bring to croutons?

Croutons for onion soup traditionally serve one role: texture. Crunchy bread contrasts with the thick, liquid broth and soft onions. Hemp flour as a coating for croutons maintains this function and adds three new values. Mattila et al. (Journal of Food Composition and Analysis, 2018) demonstrated that hemp flour contains about 30% protein and 28% dietary fiber – this is several times more than wheat flour, which has approximately 10% and 3%, respectively. Secondly, a glycemic index below 35 (Siano et al., Food Chemistry, 2019) – croutons made with hemp flour absorb more slowly. Thirdly: an intense nutty flavor that perfectly balances the sweetness of deeply caramelized onions.

Caramelization is a separate story. Onions, when heated slowly, undergo Maillard reactions and the breakdown of sucrose – they become dark golden, intensely sweet, and rich in depth of flavor that no shortcuts can replicate. 40 minutes over low heat is the minimum requirement. Onion soup tastes as it should only when the onions are truly dark and soft.

We noticed in tests that hemp flour as a coating for croutons works significantly better than plain breadcrumbs. Hemp flour adheres to the bread without the need for egg or water – just a light moistening with oil is enough. On the baking sheet, it forms a crispy crust with an intense nutty aroma that becomes particularly pronounced in the oven after about 8 minutes.

Nutritional values – what does this serving provide?

One serving of onion soup (about 300 ml) with a handful of hemp croutons (about 30 g of bread with hemp flour) provides about 260 kcal, 8 g of protein, 10 g of fat, and 32 g of carbohydrates. The fiber from the onions and hemp flour amounts to about 4 g per serving. Caramelized onions also provide quercetin – a flavonoid with antioxidant properties that concentrates during slow thermal processing.

Ingredients – what do you need?

Proportions for 4 servings. Onion caramelization time: 35–40 minutes. Soup cooking time: 20 minutes. Crouton baking time: 12 minutes.

• 800 g of onions (about 4 large onions)
• 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 1 tablespoon of lemon juice + 1 tablespoon of apple cider vinegar
• 1 sprig of fresh thyme
• 1 bay leaf
• 1 teaspoon of sugar for caramelization
• salt and pepper to taste
• 4 thick slices of bread (wheat or gluten-free) for croutons
• 2 tablespoons of hemp flour for coating the croutons
• 1 tablespoon of olive oil for the croutons
• optional: 60 g of grated gruyère or parmesan for baking

How to make onion soup with hemp croutons – step by step?

This soup requires time – mainly passive waiting while caramelizing the onions. Active work takes about 20 minutes; the rest is done by fire and time.

Step 1. Caramelize the onions. Slice the onions into thin half-moons. In a wide pot, heat butter or oil over low heat. Add the onions, salt, and sugar. Cook, stirring every 3–4 minutes, for 35–40 minutes. The onions should be dark golden and deeply sweet. Do not increase the heat – high temperatures speed up the process, they do not caramelize.

Step 2. Prepare the hemp croutons. Cut the bread into 2 cm cubes. In a bowl, mix the hemp flour with olive oil and a pinch of salt. Coat the bread cubes in the mixture. Spread them on a baking sheet. Bake at 180°C for 10–12 minutes until crispy. You can prepare the croutons in advance and store them in a container for up to 2 days.

Step 3. Build the soup. To the finished caramelized onions, add garlic and sauté for 1 minute. Pour in the wine or a mixture of juice and vinegar – reduce for 2 minutes. Pour in hot broth, add thyme and bay leaf. Simmer for 15 minutes over low heat.

Step 4. Season. Remove the thyme and bay leaf. Check the taste – the onion soup should be deeply sweet with a distinct umami note. Season with salt and pepper. If it lacks intensity – a teaspoon of soy sauce or Worcestershire sauce enhances the flavor without overpowering it.

Step 5. Serve with croutons. Pour the soup into bowls. Top with hemp croutons. Optionally, sprinkle with grated cheese and place under the broiler for 2–3 minutes. Serve immediately while the croutons are still crispy.

Tips and variations

Onion soup with hemp croutons has many variations. Here are a few tried-and-true modifications:

Vegan version. Replace butter with coconut oil or olive oil, and beef broth with vegetable stock (carrot, celery, parsley). Substitute baking cheese with nutritional yeast – it provides a similar umami flavor without dairy. Croutons made with hemp flour are inherently vegan.

Non-alcoholic version. Replace wine with a tablespoon of lemon juice and a tablespoon of apple cider vinegar. The flavor effect – acidity and aroma – is similar. You can also use 100 ml of clarified apple juice, which will add a gentle sweetness to balance the flavor.

Garlic croutons. Add a crushed garlic clove to the hemp flour and olive oil mixture. Garlic caramelizes while baking at 180°C, intensifying the flavor of the croutons. The combination of garlic, hemp flour, and baking creates an unexpectedly deep aroma.

Mistake to avoid. Do not rush the caramelization of onions. 15–20 minutes over medium heat yields golden onions, but lacking deep sweetness and caramel flavor. True caramelization requires low heat and patience – 35–40 minutes. Rushing destroys this soup more than any other mistake. Also check out our recipe for tomato soup with hemp oil – another classic Polish soup with a hemp twist.

Frequently asked questions

What does hemp flour add to onion soup croutons?

Hemp flour contains about 30% protein and 28% fiber (Mattila et al., 2018) – multiple times more than wheat flour. Croutons coated in hemp flour gain a nutty flavor that balances the sweetness of caramelized onions, and add plant protein to this otherwise low-protein soup.

How long does it take to caramelize onions?

True caramelization requires 35–40 minutes over low heat. Shortening it to 15–20 minutes yields golden and tasty onions, but without deep sweetness. Onions caramelize through Maillard reactions and sugar breakdown – both processes cannot be rushed without losing flavor quality.

Are croutons made from hemp flour gluten-free?

Hemp flour is gluten-free (GI below 35, according to Siano et al., 2019). However, croutons are made from bread – use gluten-free bread and hemp flour to ensure the entire batch is gluten-free. Hemp flour itself does not contain gluten.

How many calories are in onion soup with hemp croutons?

One serving (about 300 ml) with a handful of croutons (30 g of bread) provides about 260 kcal, 8 g of protein, 10 g of fat, and 32 g of carbohydrates. 100 g of hemp flour provides about 330 kcal, 30 g of protein, and 28 g of fiber (USDA, 2023) – which translates to about 2–3 g of extra protein per tablespoon of croutons.

What wine pairs well with onion soup?

Traditionally, dry white wine (Chardonnay, Pinot Grigio) or dry sherry is used. Wine adds acidity and aroma – the alcohol evaporates. For a non-alcoholic option: a tablespoon of lemon juice and a tablespoon of apple cider vinegar provide a similar flavor effect.

This article is for informational and educational purposes 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 · Published: 2026-05-04 · Updated: 2026-05-04