Mussel-Seaweed Butter

Recipe from Mussels by Sergio Herman

Of course, you can use this butter as a spread—it’s terrific on spelt bread, for example. But it also has other uses, such as in sauces like beurre blanc or to add to a pot of mussels before serving. Replace the butter in your recipe with this mussel butter for incredible depth of flavor—you can taste the sea.

1 pound (500 grams) mussels

3 ½ tablespoons mussel cooking liquid

1 cup (200 grams) salted butter, at room temperature 

3 ½ ounces (100 grams) salted seaweed butter, at room 

temperature (see page 229)

1 tablespoon Dijon mustard

Grated zest of 1 lemon

2 tablespoons finely chopped flat-leaf parsley

1 tablespoon finely chopped celery stalk leaves

2 tablespoons very finely chopped shallot

2 tablespoons finely chopped chives

½ teaspoon seaweed powder (available in most natural food stores or online) 

8 sea fennel (rock samphire) leaves (Crithmum maritimum) or salicornia (also called glasswort, marsh samphire, sea bean, and sea pickle—can be found in some specialty food stores), optional

Steam the mussels briefly. Fill the sink or a large pan with plenty of water and rinse the mussels. Drain, then refill with fresh water and rinse the mussels two more times. Discard any shells that float to the surface because they might be spoiled. Also discard any shells that are cracked or broken.

Bring a shallow layer of water to a boil in the pan where the steamer basket will rest. Place a dish or deep plate into the steamer basket and add the mussels. This dish will also collect the juices released during steaming. Place the lid on the steamer.

Steam the mussels for one minute, until all the shells have opened.

Take the steamer off the pan. Remove the mussels from their shells and allow them to cool slightly in the cooking liquid collected during steaming.

Transfer the mussels to a blender along with 3 ½ tablespoons of the mussel cooking liquid, both the salted and seaweed butter, mustard, and lemon zest. Blend until everything is well incorporated and the mixture is smooth, then spoon into a bowl. Add the parsley, celery stalk leaves, and shallot, and fold into the mussel-seaweed butter.

Mound the butter onto a plate or dish, and mold it into an attractive shape. Finish with the chives, seaweed powder, and sea fennel (if using).