Celeriac Soup with Hazelnut Crumble

I discovered celeriac soup on a grey autumn afternoon when I had no idea what to do with a knobby root vegetable sitting in my crisper drawer. A friend had left it behind after a farmers market haul, and honestly, it intimidated me—all those bumps and strange angles. But one evening, hunger and curiosity won out, and I roasted it with nothing but oil and salt, expecting something modest. What emerged from the oven was transformative: sweet, earthy, almost caramel-like. The moment I blended it into silk and topped it with those toasted hazelnuts, I understood why this humble vegetable deserves far more respect.

I made this soup for my partner on a Sunday when the kitchen felt cold and the day needed warming. He came home tired from work, and I had this steaming bowl waiting—the aroma of roasted earth and toasted nuts filling the whole apartment. Watching him taste it, then close his eyes for a second, that moment made me realize soup isn't really about feeding someone; it's about caring for them in a way that feels effortless but tastes like intention.

Ingredients

• Celeriac (700 g), peeled and cubed: This knobbly root vegetable is the soul of the soup, delivering an earthy, subtly sweet flavor that deepens when roasted; don't skip the roasting step, as it's what transforms it from mild to memorable.
• Potato (150 g), peeled and diced: Adds starch and body to help create that silky texture without relying solely on cream.
• Onion (1 medium), chopped: Builds the flavor foundation; medium heat and patience coax out its natural sweetness.
• Garlic (2 cloves), minced: A quiet player that deepens the savory notes without shouting.
• Vegetable broth (900 ml): Use a good quality broth if you can; it's worth the difference.
• Olive oil (2 tbsp total): One portion goes on the celeriac for roasting, the other starts the soup base.
• Heavy cream or plant-based alternative (100 ml): Optional but transforms the soup into something special; swirl it in at the end for a silkier mouthfeel.
• Ground white pepper (1/2 tsp) and salt: White pepper keeps the soup visually pristine while delivering gentle heat.
• Hazelnuts (70 g), roughly chopped: Toast these until golden—they become sweeter and more complex when heat brings out their oils.
• Unsalted butter or plant-based margarine (1 tbsp): Coats the hazelnuts and makes them cling together slightly as they cool.
• Fresh parsley (1 tbsp), finely chopped: A fresh finish that feels like sunlight on top of the earthy soup.

Instructions

Preheat and prepare your vegetables:

Set your oven to 200°C and get all your vegetables prepped while it heats up; this is where mise en place saves you time and stress later.

Roast the celeriac until golden:

Toss the cubed celeriac with a tablespoon of olive oil, salt, and pepper, then spread it on a baking tray. Roast for 25–30 minutes, turning halfway through, until the edges turn golden and the flesh becomes completely tender. You'll know it's ready when a fork slides through easily and the kitchen smells like caramelized earth.

Build the soup base while celeriac roasts:

Heat the remaining tablespoon of oil in a large pot over medium heat, then add your chopped onion. Let it soften and turn translucent, about 4 minutes, then add the minced garlic and diced potato. Cook for another couple of minutes just to marry the flavors slightly.

Combine and simmer:

Add the roasted celeriac to the pot along with the vegetable broth, bring it to a gentle boil, then lower the heat and let it simmer quietly for 15–20 minutes until all the vegetables are completely soft and easily mashable. This isn't a rushed step; let the flavors mellow together.

Toast the hazelnuts for the crumble:

While the soup simmers, place your roughly chopped hazelnuts in a dry skillet over medium heat. Toast them for 3–4 minutes, stirring occasionally, until they release their aroma and turn a shade darker. Add the butter and sea salt, stirring gently until the nuts are coated and golden, then remove from heat and let cool slightly on a plate so they firm up a bit.

Blend the soup into silky submission:

Using an immersion blender, purée the soup directly in the pot until it's velvety smooth, working carefully as hot soup splashes easily. If you prefer to use a countertop blender, work in batches and don't fill it more than halfway. Stir in the cream if you're using it, then taste and adjust the salt and white pepper until it feels just right.

Serve with swagger:

Ladle the soup into bowls, then crown each one generously with the hazelnut crumble and a scatter of fresh parsley. The contrast between the smooth soup and crunchy topping is what makes this dish feel special rather than simple.

Save

There's something about serving this soup that makes people slow down and notice what they're eating. My mother, who claims not to like vegetables, had three bowls without realizing it, and afterward she asked for the recipe—not to make it herself, but to ask me to make it again. That's when I knew this wasn't just another soup; it was a conversation starter.

The Magic of Roasting Root Vegetables

Roasting is what separates a forgettable soup from one worth talking about. When you roast celeriac, its natural sugars caramelize slightly, deepening its earthy personality and adding sweetness that doesn't need honey or cream to shine. I learned this by accident, really—I'd planned to boil everything and got distracted, then decided to pop the celeriac in the oven while prepping other things. That mistake became the entire point of the recipe. The same principle works for any root vegetable you're turning into soup; a little time in the oven changes everything.

Why Hazelnuts Matter More Than You Think

A smooth soup alone can feel incomplete, almost apologetic. The hazelnut crumble is the punctuation mark that turns it into something confident and textured. Hazelnuts specifically have this quiet sophistication—they're not as bold as walnuts or as delicate as almonds, striking a balance that complements earthy celeriac perfectly. Toasting them awakens oils that have been dormant, making them taste almost buttery and complex. I once tried making this with store-bought hazelnut brittle, thinking I was being clever, and it was completely wrong—the crumble needs to be fresh and warm, so the butter coats everything and the salt makes itself known with each bite.

Customizing Without Losing Your Way

This soup is forgiving in ways that feel permissive. You can add a whisper of fresh thyme while it simmers, or finish each bowl with a small squeeze of lemon juice—both brighten the earthiness without overpowering it. Some people love a pinch of nutmeg stirred in near the end; others prefer it pure and unapologetic. The cream is truly optional; if you skip it, the soup is lighter but still utterly satisfying. If you're cooking for vegans or anyone avoiding dairy, plant-based cream and margarine work beautifully—I've made it both ways and honestly can't choose a favorite.

• A dry white wine like Pinot Gris is the perfect pairing if you're making this for dinner rather than lunch.
• You can make the soup a day or two ahead and reheat it gently; just toast fresh hazelnuts on serving day so they stay crisp.
• Leftover hazelnut crumble keeps in an airtight container for nearly a week and makes a surprisingly good addition to salads or roasted vegetables.

Save

This soup has become my quiet anchor on difficult weeks—something I make when I need to remember that nourishment and comfort are often the same thing. It asks very little and gives back generously.

Recipe FAQs

→ Can I make this ahead of time?

Absolutely. Prepare the base up to 2 days ahead and refrigerate. The hazelnut crumble stays fresh in an airtight container for 3 days. Reheat gently, adding a splash of broth if thickened, and top with fresh crumble before serving.

→ What can I substitute for hazelnuts?

Walnuts, pecans, or toasted pumpkin seeds work beautifully. Each brings different nutty notes—walnuts offer earthiness, pecans add sweetness, while pumpkin seeds provide a lighter crunch and nut-free alternative.

→ Is this suitable for freezing?

Yes, freeze the soup base without cream for up to 3 months. Thaw overnight in the refrigerator, reheat slowly, then stir in cream and fresh hazelnut topping. The crumble never freezes well, so always prepare fresh.

→ How do I achieve the smoothest texture?

Roast celeriac until completely tender—this breaks down fibers for easier blending. Use a high-powered blender and strain through a fine-mesh sieve for absolute silkiness. Adding potato naturally thickens and smooths without heavy cream.

→ Can I use raw celeriac instead of roasting?

While possible, you'll miss the caramelized depth that roasting provides. Raw celeriac yields a milder, slightly bitter flavor. If skipping the oven, sauté longer until golden before simmering to develop some sweetness.