📌 Potato Gratin with Salmon and Homemade Béchamel

Posted 2 April 2026 by: Admin #Recipes

Prep Time

20 minutes

Cook Time

45 minutes

Total Time

1 hour 05

Servings

4 servings

Potato and salmon gratin is a dish that deserves to be taken seriously. Not because it’s complicated — it’s not. But because when it’s done right, with a béchamel that truly coats everything and potatoes that melt under the fork, people around the table reach for seconds without even thinking about it.

Final result — The gratin comes out of the oven with a beautifully browned top — that moment when the cheese is crispy and the whole house smells amazing.

What you see there is a light caramel-colored crust that cracks slightly as the spoon sinks in. Underneath, the layers reveal themselves: glistening potatoes, pink salmon enveloped in creamy sauce, all gently collapsing onto the plate. The aroma rising up is that mix of grilled cheese and warm butter, with a briny undertone that never quite disappears. The first forkful goes all the way to the bottom of the dish.

Why you’ll love this recipe

✓Everything can be prepared the day before : Assemble the gratin, cover it in the fridge, and bake it the next day. The flavors will be even more melded and the béchamel better absorbed by the potatoes.

✓Five ingredients do 90% of the work : Potatoes, salmon, butter, milk, cheese. No endless list, no hard-to-find products. What makes this dish good is the technique, not the ingredients.

✓It stands alone as a main course : No need for an elaborate side dish. A green salad with whole-grain mustard is more than enough. This gratin is truly nourishing.

✓The oven does the work for you : Once assembly is finished, you place the dish in the oven and forget about it for 45 minutes. This is precisely why it’s ideal when you’re hosting.

Ingredient Notes

Ingredients

Few ingredients, lots of character: waxy potatoes, salmon, and a homemade béchamel that makes all the difference.

The potatoes : Charlotte or Monalisa, no negotiating on that. These waxy varieties hold up during cooking without turning into mash. Bintje is for fries. Count about 600 g for 4 people — 3 large potatoes.
The salmon : Smoked salmon is the simplest and works very well. It’s already salted, so go easy on seasoning the béchamel. If you prefer fresh salmon, poach it for 5 minutes in a little boiling water before flaking it — it will be milder and less briny.
The grated cheese : Emmental for melting, Comté for flavor. A mix of both is ideal. Avoid pre-shredded cheese in bags: it contains anti-caking starch that prevents it from browning well. Grate it yourself; it takes two minutes.
The butter and flour : Equal parts roux: 50 g butter, 50 g flour. Preferably unsalted butter — not semi-salted — to better control the final seasoning. Ordinary all-purpose flour is perfectly fine.
The nutmeg : A pinch, no more. It’s the kind of detail people don’t consciously notice but miss when it’s absent. Freshly grated if possible; powdered nutmeg loses intensity quickly.

Slice the potatoes to the thickness of a two-euro coin

Peel the potatoes and slice them into thin rounds, about 3 mm. Use a mandoline if you have one, or a knife if you have the patience. Thickness isn’t about aesthetics: slices that are too thick will remain firm in the center even after 45 minutes in the oven. Rinse them quickly under cold water to remove excess starch, then dry them in a clean kitchen towel. A step many skip, wrongly — dry potatoes absorb the béchamel better and hold together in the dish instead of sliding around.

Whisk without stopping — really, without stopping

Béchamel is simple, but it demands your complete presence for five minutes. Melt the butter over low heat until it foams slightly, add the flour all at once, and stir for two minutes — the roux should smell like toasted hazelnuts, not raw flour. Pour in the cold milk in a thin stream while whisking continuously. Lumps appear exactly when you look away. The sauce is ready when it coats the back of a spoon and slides slowly when you tilt the pan. Add the nutmeg, taste, then salt, keeping in mind that the salmon is already salty.

Assemble the layers without rushing

Preheat the oven to 180°C. Butter the bottom of the dish — this prevents the bottom potatoes from sticking. The logic of assembly: potatoes, salmon, béchamel, and repeat. No need to measure each layer. The final layer must be béchamel, followed by a generous coating of grated cheese over the entire surface. Press down lightly at each level to remove air pockets. Aim for 3 to 4 cm in height in the dish — a gratin that is too thin dries out, while one that is too thick stays raw in the center.

Don’t open the oven before 40 minutes

Place it in the oven and resist the urge to check every ten minutes. The oven is working; let it do its job. At 40 minutes, take a peek: the top should start to take on that light caramel hue that signals it’s almost ready. Five more minutes if the cheese isn’t colored yet. Pierce the center with the tip of a knife — it should sink in without resistance all the way to the bottom. Remove the dish and let it rest for 10 minutes before serving. This rest is important: the gratin holds together better when sliced and the layers don’t collapse on the plate.

Tips & Tricks

If using smoked salmon, taste the béchamel before salting — the salmon releases salt during cooking and you could end up with an oversalted dish without realizing it.
A tablespoon of heavy cream added to the béchamel at the end of cooking completely changes the texture of the sauce — silkier, rounder. It’s not mandatory, but it’s the difference between good and very good.
The gratin prepares very well the day before. Assemble it completely, wrap it in the fridge, and bake it the next day directly from the cold, adding 10 extra minutes of cooking time.

Close-up — The first spoonful that breaks the crust: the cheese stretches, the béchamel flows, the potatoes melt.

FAQs

Can I prepare this gratin the day before?

Yes, it is even recommended. Assemble the gratin entirely, cover it with plastic wrap, and keep it in the refrigerator until the next day. Bake it directly from the cold, adding 10 extra minutes of cooking time to compensate for the starting temperature.

Smoked salmon or fresh salmon, which is the better option?

Both work, but smoked salmon is simpler and more flavorful. If using fresh salmon, poach it for 5 minutes in simmering water before incorporating it. Note in both cases: smoked salmon is already salty, so taste your béchamel before seasoning.

How to avoid lumps in the béchamel?

Pour the cold milk in a very thin stream while whisking without interruption. The cold milk versus the heat of the roux is what causes lumps when poured too quickly. If lumps appear anyway, a quick burst with an immersion blender fixes the problem in 10 seconds.

Can this gratin be frozen?

Yes, both before and after cooking. Before cooking, freeze it wrapped for up to 2 months and bake it still frozen at 160°C for 1h15. After cooking, cut it into individual portions for easier thawing — reheat in the oven at 180°C rather than the microwave to regain the crispness.

Do the potatoes need to be pre-cooked?

No, it’s not necessary if you slice them thinly (3 mm). Pre-cooking for 5 to 10 minutes in water can be useful if using firmer varieties or if you are in a hurry, but with thinly sliced Charlotte or Monalisa, the oven is more than enough in 45 minutes.

What can I substitute for cheese if I don’t have Emmental?

Grated Parmesan for a crispier and saltier crust, Gruyère for something close to Emmental, or mild Cheddar for a different touch. What you should avoid is store-bought bagged shredded cheese: it contains starch that prevents it from browning well.