The herb butter is the whole recipe, and it takes about two minutes to make. Butter, chopped cilantro and chervil, a little crustless bread and lemon juice, blitzed together and chilled into a sheet. It goes on the back of a cod fillet, the fillet goes into a hot oven for ten minutes, and the bread in the butter crisps into a crust as the butter melts down into the fish. Around it: baby spring vegetables and cockles opened on a plancha. Bordier puts the preparation at 30 minutes.
At a glance
- Difficulty: Medium
- Serves: 4
- Active time: 30 minutes
- Cook: 10 minutes at 180°C / 356°F (gas mark 6), plus 2 minutes for the cockles
- Key ingredient: Smoked Salt Bordier Butter
Why this works
Cod is a lean, mild fish that dries out quickly and does not season itself. The classic answer is a croute d'herbes, a butter and breadcrumb crust laid over the fillet, and that is what this is. As the oven heats the crust, the butter melts and runs down into the flesh, basting it continuously, while the bread and herbs above stay dry enough to brown. Ten minutes is short by design: a fillet of this size is done the moment the flesh turns opaque and separates into flakes under gentle pressure.
The smoked salt butter carries the idea further. A smoked butter against cod and cockles is a Breton coastal logic rather than a novelty. It reads as the smoke of a shoreline fire against shellfish, and it means the crust arrives seasoned without a separate salting step. Bordier's butters are churned by hand in Brittany on a traditional wooden malaxeur, which leaves them denser and more plastic than industrial butter, and that matters here: the herb butter has to be spreadable enough to blitz and firm enough to hold a sheet between parchment in the fridge. The sauce is separate and lighter, built by sweating shallots in the juice released by the cockles and emulsifying it with lemon.
Ingredients
Bordier calls for cockles, but littleneck clams are the better bet at a US fish counter and the recipe says so explicitly.
| Ingredient | Metric | US |
|---|---|---|
| Fresh cod | 600 g | 1 1/3 lb (21 oz) |
| Cockles or littleneck clams (a good 15 of them used for their juice) | About 30 | About 30 |
| Chopped herbs (cilantro, chervil) | 100 g | 1/4 lb (3.5 oz) |
| Smoked salt Bordier butter, at room temperature | 100 g | 1/4 lb (3.5 oz) |
| Bread, crusts removed | 50 g | 1 3/4 oz |
| Lemon, juiced | 1 | 1 |
| Baby carrots with their greens | 4 | 4 |
| Baby leeks | 4 | 4 |
| Baby fennel | 4 | 4 |
| New turnips | 4 | 4 |
| Green onions | 4 | 4 |
| Cockle or clam juice | From the cockles | From the cockles |
| Shallots | Quantity not specified | See the FAQ below |
| Salt and pepper | To taste | To taste |
Method
Step 1: Make the herb butter
Blend the butter, the chopped herbs, the crustless bread and the lemon juice together. Spread the mixture out between two sheets of parchment paper and refrigerate it until firm.
Step 2: Cook the vegetables and build the sauce
Boil the baby vegetables in separate pans, then finish them in a dab of smoked salt butter. For the shallot sauce, sweat the shallots with the juice from the cockles and emulsify with lemon juice.
Step 3: Bake the cod under its crust
Lay the sheet of herb butter over the back of the cod and bake for 10 minutes in an oven preheated to 180°C / 356°F (gas mark 6).
Step 4: Open the cockles and plate
Set the cod and the vegetables out on a large serving platter. Open the cockles on a plancha for 2 minutes, add them to the platter, and spoon the sauce over everything.
Tips from our kitchen
- Purge the cockles before you cook them. An hour in cold salted water lets them spit out their sand. Any that stay open when tapped are dead and go in the bin, and any that refuse to open on the plancha go the same way. Sand ruins this dish faster than anything else.
- Reserve butter for the vegetables. Bordier gives 100 g as one figure but uses the butter twice, in the herb crust and to finish the vegetables. Our guidance is to keep about 80 g for the crust and 20 g for the pan. The same applies to the lemon: split the juice of the one lemon between the herb butter and the sauce.
- Roll the herb butter thin and chill it hard. Between two sheets of parchment, take it down to about 3 mm and leave it in the fridge until solid. A firm sheet can be cut to the exact footprint of the fillet and laid on cleanly. Soft butter slides off the fish in the oven and burns on the tray.
- Use dry bread, not fresh. Fresh crumb turns the butter into a paste that steams rather than crisps. Day-old bread with the crusts cut away, blitzed into the butter, is what gives you a crust that browns.
- Ten minutes is for a thick fillet. Cod at 600 g for four means a piece roughly an inch at the thickest point. Check at eight minutes: the flesh should be opaque and just parting into flakes when you press it. Cod carries on cooking off the heat, so pull it slightly early.
- No plancha, no problem. A dry cast-iron pan over high heat opens cockles just as well. Cover it for the two minutes so the steam works with the heat, and catch the juice that runs out, because that juice is the base of the sauce.
How to serve it
Bring it to the table on one large platter and let people help themselves, which is how Bordier presents it and how it eats best. It needs nothing more than bread and a dry white with some salinity, a Muscadet or a Picpoul. If you like the pairing of butter and shellfish, our guide to La Brújula Spanish conservas covers tinned cockles and clams that make a decent year-round stand-in when fresh ones are out of season.
Where to buy Bordier butter in the US
The French Pantry ships Bordier butter across the United States in insulated overnight packaging, straight from the workshop in Brittany.
This recipe traditionally uses Bordier's smoked salt butter, which we no longer carry. The closest substitute in our range is the semi-salted butter, which brings the same salinity and the same dense hand-churned texture to the herb crust, without the smoke.
- Churned Salted Butter by Bordier (4.4 oz): the demi-sel, semi-salted at 2.8% fine salt, and our recommended substitute here.
For the flavoured butters and the rest of the range, browse the Maison Bordier collection.
Frequently asked questions
How much butter do I need for this recipe?
The recipe calls for 100 g. A Bordier block is 4.4 oz (125 g), so one block covers the herb crust and the vegetables with a little to spare.
What should I use instead of smoked salt butter?
Use Bordier's semi-salted butter. If you want the smoke back, add a small pinch of smoked sea salt to the herb butter when you blitz it, and taste before you add more, because smoked salt is far stronger than it looks. Bordier's seaweed butter is the other option worth considering: it does not smell of smoke, but its iodised character sits very naturally against cod and cockles.
How many shallots does the sauce need?
Bordier lists shallots without a quantity. Our guidance is two, finely sliced, for four servings. Sweat them gently in a little butter until soft and translucent but not coloured, then add the cockle juice.
How should I store the butter?
Keep it wrapped and refrigerated, and cut only what you need. It absorbs other smells readily, so keep it away from strong cheese and anything cured. Press the paper back onto the cut face after each use.
Does Bordier butter need refrigeration?
Yes. Bordier butter is a fresh, hand-churned product and ships cold. Refrigerate it as soon as it arrives. For this recipe you want it at room temperature to blend the herb butter, so take it out about an hour ahead.
Can I make the herb butter in advance?
Yes, and it is the sensible way to run this dish. The sheet keeps three or four days in the fridge between its parchment, or a month in the freezer. Cut it straight from cold and lay it on the fish.
Related reading
- Bordier Butter: What It Is, Why Chefs Love It, and How to Use It
- How to Choose Your French Butter: A Buyer's Guide
- La Brújula Spanish Conservas
Recipe and photograph adapted from Maison Bordier, with thanks. The French Pantry is an authorized US retailer of Bordier butter.