Name: Vegetarian French Onion Soup with Spiralized Onions Recipe
Prep time: 20 min
Cook time: 1 h 50 min
Total time: 2 h 10 min
Cuisine: French
Ingredients: 1 kg onions (approximately 6 medium onions, spiralized); 40 g butter; 2 tsp brown sugar; 4 cloves garlic (crushed); 2 Tbsp plain white flour; 250 ml dry white wine; 950 ml vegetable stock or broth; 2 tsp soy sauce; 1 tsp marmite; 2 bay leaves; A few small sprigs of rosemary (optional, for garnish); Baguette slices (2 per serving); 1/2 cup grated Gruyere cheese

Jump to Recipe· 4.3 from 66 reviews

If you adore the rich, comforting flavors of classic French onion soup but want a lighter, meat-free twist, then you are going to fall head over heels for this Vegetarian French Onion Soup with Spiralized Onions Recipe. It’s a beautiful, soulful bowl of caramelized onions cooked low and slow to bring out their natural sweetness, all enhanced by the delicate texture that spiralizing provides. This recipe transforms simple pantry staples into a luxurious, deeply flavorful soup, perfect for cozy evenings or impressing dinner guests with minimal fuss. Trust me, once you try this version, you’ll never look back.

Ingredients You’ll Need

The image shows a white spiralizer machine on a white marbled surface, with thin, long, curly white vegetable noodles coming out from the side. The vegetable, held in place by the machine's white clamp, is being turned into many delicate, translucent strands that curl and pile up loosely around the spiralizer. The background is dark, which contrasts with the bright white of the spiralizer and vegetable noodles, highlighting their texture and shape. photo taken with an iphone --ar 4:5 --v 7

Gathering your ingredients is an exciting first step because these few essentials all bring something special to your soup. Each element plays a key role, from the sweetness of the caramelized onions to the savory umami depth from soy sauce and marmite, resulting in a sophisticated vegetarian broth that sings with flavor.

Onions (1 kg): Spiralized for tender, silky strands that caramelize beautifully and cook faster than typical slices.
Butter (40 g): Adds richness and helps caramelize the onions to golden perfection.
Brown sugar (2 tsp): Enhances the natural sweetness of the onions without overpowering.
Garlic cloves (4, crushed): Introduces fragrant warmth for depth and complexity.
Plain white flour (2 Tbsp): Classic thickener that helps create a luscious, silky soup base.
Dry white wine (250 ml): Deglazes the pan and adds bright acidity to balance the sweetness.
Vegetable stock (950 ml): The hearty liquid foundation; choose a flavorful broth for best results.
Soy sauce (2 tsp): A vegetarian secret weapon for umami and a touch of saltiness.
Marmite (1 tsp): Boosts complexity with its rich, yeasty savoriness without overwhelming.
Bay leaves (2): Infuse a subtle herbal note during the simmer.
Baguette slices: Crunchy, toasted bread perfect for soaking up the soup.
Grated Gruyere cheese (½ cup): Melts into gooey, golden goodness atop the toasted baguette slices for that iconic finish.
Sprigs of rosemary (optional): Adds a fresh, aromatic garnish for a vibrant touch.

How to Make Vegetarian French Onion Soup with Spiralized Onions Recipe

Step 1: Spiralize the Onions

Begin by spiralizing your onions—this technique not only saves time but also creates those long, tender ribbons that caramelize evenly and deliver a unique texture in every spoonful. It is quite a fun step and makes the cooking process feel special right from the start.

Step 2: Caramelize the Onions

In a large, heavy pan over low heat, melt your butter before tossing in all the spiralized onions along with the brown sugar. Give it a good stir to coat every strand in butter and sugar, then cover the pan and let it do its magic on the lowest heat setting for at least an hour. Remember to stir about every 15 minutes—this slow caramelizing is where your soup’s deep, sweet flavor develops, turning the onions a gorgeous golden brown.

Step 3: Add Garlic and Flour

Once your onions are perfectly caramelized, stir in the crushed garlic just for a minute until fragrant—this tiny burst of garlicky aroma will enhance the overall flavor without overpowering. Then sprinkle in the flour and mix well to combine, helping to create that creamy texture we all love in a French onion soup.

Step 4: Deglaze with White Wine

Pour in the dry white wine and turn up the heat so it bubbles and reduces slightly. This step pulls up all the lovely browned bits from the bottom of the pan and adds a fresh, acidic balance to the rich onion flavor.

Step 5: Add Stock, Soy Sauce, Marmite, and Bay Leaves

Next, stir in the vegetable stock, soy sauce, marmite, and bay leaves. These ingredients bring bold umami notes and complexity, rounding out the flavor profile and turning the soup into a rich, savory masterpiece. Once combined, reduce heat to a simmer and let it cook gently for another hour or until you’re ready to serve.

Step 6: Prepare the Toppings

While the soup simmers, toast your baguette slices so they’re crisp but still sturdy enough to hold the melted cheese. Have your grated Gruyere ready to pile on generously just before serving.

Step 7: Serve and Grill

Ladle the aromatic soup into bowls, top with toasted baguette slices, and heap on the grated Gruyere cheese. Pop the bowls under a grill for a few minutes until the cheese melts into irresistible, bubbling, golden perfection—this is the crowning glory of the Vegetarian French Onion Soup with Spiralized Onions Recipe.

How to Serve Vegetarian French Onion Soup with Spiralized Onions Recipe

A close-up image shows a wooden cup filled with light brown soup that appears smooth with small chunky bits. Above the cup, a spoon holds a portion of the soup with translucent and slightly shiny thin noodle strands and soft small pieces, dripping back into the cup. The cup sits on a white marbled surface, with the wooden handle visible on the right side. The photo is softly lit with a shallow depth of field, focused on the soup in the spoon. Photo taken with an iphone --ar 4:5 --v 7

Garnishes

Fresh herbs such as small sprigs of rosemary add a lovely aromatic hint and a pop of color that makes the soup look as good as it tastes. Sprinkle a pinch of cracked black pepper or a few fresh thyme leaves for additional layers of flavor. These small touches elevate your presentation and entice the senses.

Side Dishes

This soup shines as a satisfying main dish when paired with a crisp green salad dressed with lemon vinaigrette or some roasted vegetables for a well-rounded meal. For a heartier spread, serve alongside a light cheese plate or crusty bread to scoop up every drop.

Creative Ways to Present

Try serving the soup in individual oven-safe crocks for a rustic, charming feel. You can also experiment with different types of cheese toppings such as fontina or mozzarella, or add caramelized shallots on top for an extra layer of elegance. For a dramatic effect, garnish with edible flowers when entertaining guests.

Make Ahead and Storage

Storing Leftovers

Your leftover Vegetarian French Onion Soup with Spiralized Onions Recipe keeps beautifully in the fridge for up to four days. Store it in an airtight container to preserve its rich flavor and aroma. Reheat gently on the stove to avoid losing any of the soup’s velvety texture.

Freezing

If you want to save this delicious soup for longer, it freezes really well. Portion it out into freezer-safe containers, leaving some headspace as the liquid will expand. When ready, thaw overnight in the fridge before reheating to maintain that freshly made taste.

Reheating

Reheat the soup on the stovetop over low-medium heat, stirring occasionally. If it looks too thick, add a splash of vegetable stock or water to loosen it up. When serving, add fresh baguette and Gruyere cheese on top and grill again to recapture that fresh-out-of-the-oven magic.

FAQs

Can I use any type of onion for this soup?

Absolutely! Yellow onions are the classic choice for their balanced sweetness and flavor, but you can mix in some white or red onions to add different notes and colors. Just be sure to spiralize them to keep the texture consistent.

Is this soup gluten-free?

The recipe as written uses plain white flour and baguette slices, which contain gluten. You can easily substitute the flour with a gluten-free alternative and serve with gluten-free bread to make the whole dish gluten-free.

What can I use instead of marmite?

If you don’t have marmite on hand or prefer a milder taste, you can swap it for miso paste or vegan Worcestershire sauce. Both options will provide that essential umami punch without changing the character of the soup too much.

Can I make this soup without wine?

Yes! If you prefer not to use wine, substitute it with additional vegetable stock plus a splash of lemon juice or apple cider vinegar to mimic the acidity and depth that wine lends to the dish.

How do spiralized onions change the soup?

Spiralizing onions transforms their texture into long, delicate ribbons that caramelize faster and more evenly, resulting in a silkier mouthfeel and a visually stunning soup. It’s a clever twist that elevates the traditional dish.

Final Thoughts

I genuinely can’t recommend this Vegetarian French Onion Soup with Spiralized Onions Recipe enough. It takes a familiar classic and breathes new life into it with a clever spiralized twist and deeply layered flavors. Whether you’re cooking for friends, family, or simply treating yourself, this soup is the kind of warm hug in a bowl that keeps you coming back for more. So go ahead, grab those spiralizers, and dive into this delicious bowl of comfort—you won’t regret it!