Celeriac Soup with Hazelnut Crumble

There's something almost magical about how celeriac transforms when it hits the oven—all those earthy, slightly nutty flavors deepen and sweeten as the edges turn golden. I discovered this soup on a grey autumn afternoon when I had half a celeriac sitting in my vegetable drawer and absolutely no idea what to do with it. A friend casually mentioned roasting it first, and that one suggestion changed everything about how I approached this vegetable.

I made this for my partner on a Sunday when we were both tired and wanted something that felt fancy without the fuss. He came into the kitchen just as the hazelnuts were toasting, and that smell alone made him stop what he was doing. It became our favorite quiet-evening meal, the kind where you don't need to talk much because the food is doing the talking for you.

Ingredients

• Celeriac (1 large, about 700 g): This knobby root is the star, and roasting it first makes all the difference—it develops a sweetness you won't find in raw preparations.
• Onion (1 medium): The aromatic base that softens and becomes almost invisible in the final blend.
• Garlic (2 cloves): Just enough to add warmth without overwhelming the delicate celeriac flavor.
• Potato (1 medium, about 150 g): This adds body and helps create that silky texture without needing cream.
• Vegetable broth (900 ml): Use one you actually like drinking—it matters more than you'd think when it's the main liquid.
• Olive oil (2 tbsp total): Keep it good quality; it's one of only a few things you'll actually taste.
• Heavy cream or plant-based alternative (100 ml): Optional but recommended—it adds a luxurious finish, though the soup is delicious without it.
• White pepper (1/2 tsp): White pepper is gentler and less visible than black, letting the celeriac shine.
• Salt: Taste as you go—you'll need more than you think.
• Whole hazelnuts (70 g): Buy them with skins on if you can; there's more flavor there and the crumble looks more rustic.
• Unsalted butter or plant-based margarine (1 tbsp): This coats the hazelnuts and helps them turn golden and crisp.
• Sea salt (1/4 tsp): For the crumble topping—a different salt gives it distinction.
• Fresh parsley (1 tbsp): A bright green finish that's optional but worth the small effort.

Instructions

Get your oven ready and prep the star ingredient:

Preheat to 200°C and while it's warming, peel your celeriac—it's easier than it looks if you use a sharp knife. Cube it into roughly even pieces so everything cooks at the same rate.

Roast the celeriac until it's golden and soft:

Toss your cubes with 1 tablespoon of olive oil, a pinch of salt, and white pepper, then spread them on a baking tray in a single layer. You want them to roast for 25 to 30 minutes, turning them halfway through so they get golden on all sides—this is where the real flavor happens.

Start building flavor in your pot:

While the celeriac is in the oven, heat your remaining tablespoon of olive oil in a large pot over medium heat. Add your chopped onion and let it soften for about 4 minutes until it becomes translucent and fragrant. Stir in the minced garlic and diced potato, cooking for just another 2 minutes until everything smells amazing.

Combine and simmer until everything is tender:

When the roasted celeriac comes out of the oven, add it to the pot along with your vegetable broth. Bring it to a gentle boil, then lower the heat and let it simmer for 15 to 20 minutes until all the vegetables are so soft they practically fall apart when you touch them.

Toast your hazelnuts while the soup cooks:

In a separate skillet over medium heat, toast your roughly chopped hazelnuts dry for about 3 to 4 minutes, stirring occasionally, until they smell toasty and warm. Add your butter and sea salt, tossing everything together until the nuts are golden and glossy, then set aside to cool slightly—they'll crisp up as they cool.

Blend until the soup becomes silky smooth:

Using an immersion blender, purée your soup right in the pot until it reaches that velvety, smooth texture you're after. If you don't have an immersion blender, carefully work in batches with a countertop blender, letting it cool slightly between batches. Stir in your cream if you're using it, then taste and adjust your seasoning—you might want more salt than you expect.

Serve with crunch and brightness:

Ladle the soup into bowls and top each one generously with your hazelnut crumble. A small handful of fresh parsley scattered on top adds color and a fresh finish.

Pin It

There was one evening when a friend who usually avoids creamy soups came over, and I almost apologized before serving this. She took one spoonful, paused, and asked what was in it—that moment of someone being genuinely surprised by something you've made is exactly why I keep making this soup.

The Roasting Secret

Most people boil their celeriac or roast it quickly and move on, but this soup proves that roasting for a full 25 to 30 minutes actually matters. When celeriac roasts, the natural sugars caramelize slightly, and that deep, almost chestnut-like sweetness is what makes people taste this soup and wonder what you've done differently. The texture also changes—roasted celeriac becomes fluffy and almost creamy on the inside, which means your soup will be silkier even without cream.

Building Depth Without Cream

I made this soup vegan for a dinner party once and realized the cream isn't actually essential—the roasted celeriac and potato already create enough body that the soup feels luxurious. The hazelnut crumble is really what makes the texture interesting; that contrast between silky soup and crispy, buttery nuts is what people remember. If you do add cream, use it sparingly and stir it in gently so you can taste the celeriac itself.

Variations and Final Touches

This soup is genuinely flexible, which is one of the reasons I've made it so many times. Once you understand the basic technique, you can play with additions based on what you have or what mood you're in. A squeeze of fresh lemon brightens everything right at the end, and a small pinch of fresh thyme stirred in just before serving adds an earthy, herbaceous note that feels unexpected.

• Try a drizzle of truffle oil on top instead of parsley if you want to elevate it for guests.
• Swap half the hazelnuts for toasted walnuts for a slightly more bitter, complex crumble.
• Add a small splash of brandy or dry sherry when you add the broth for subtle depth.

Pin It

There's something deeply satisfying about a soup that takes about an hour from start to finish but tastes like you've been thinking about it all day. This one has become my answer when someone asks what to make when you want to feel taken care of without actually fussing.

Recipe FAQs

→ Can I make this soup ahead of time?

Absolutely. Prepare the soup base up to 2 days in advance and refrigerate. Reheat gently over medium-low heat, adding a splash of broth if needed. Prepare the hazelnut crumble fresh just before serving for optimal crunch.

→ What can I substitute for celeriac?

Parsnips or cauliflower work well as alternatives, though celeriac provides that distinctive earthy flavor profile. The texture and cooking time remain similar, making substitutions straightforward.

→ Is freezing recommended?

Yes, freeze the cooled soup base in airtight containers for up to 3 months. Thaw overnight in the refrigerator. The hazelnut crumble should be stored separately at room temperature and added fresh after reheating.

→ How do I achieve the smoothest texture?

Roasting the celeriac first softens the fibers significantly. Use an immersion blender for several minutes, or pass the soup through a fine-mesh sieve after blending for restaurant-quality silkiness.

→ Can I make this vegan?

Certainly. Simply replace heavy cream with coconut cream, cashew cream, or oat milk. Use plant-based margarine instead of butter in the hazelnut crumble. The result remains equally delicious and creamy.