Per the New York Times’ former longtime food critic Craig Claiborne, billi bi is “the most elegant and delicious soup ever created.”
I’m inclined to agree. The creamy, mussels-studded French invention (created, allegedly, by Norman chef Louis Barthe and named for a favored restaurant patron called Billy) is the very picture of refinement, whether it’s served up in petite portions for a first course or in heartier bowls for a sumptuous meal.
But perhaps the best thing about billi bi is that its elegance comes near effortlessly.
The recipe is simple—steam mussels in wine, water, herbs, and alliums until the shells open; shuck them (it takes 5 minutes, tops); and strain the broth.
Whisk together cream and a couple egg yolks—a French trick called a liaison, which is responsible for the soup’s unbeatably lush texture—and stir the combo into the broth to enrich it.
Divide the mussels into serving bowls, pour the creamy soup over them, and prepare for company to be wowed.
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Since the recipe was so quick and easy to make, I was able to churn out several batches of billi bi in no time, which allowed me to quickly refine the amount of wine (I wanted just enough crisp acidity to offset the cream without overpowering the seafood), the seasoning (dried thyme and a pinch of cayenne), and the types of alliums (onion in the broth; chives as a garnish).
I encountered only one recurring problem along the way: The yolks in the liaison had a tendency to curdle as I heated the soup to serving temperature, which turned the lush soup lumpy.
But omitting the liaison was out of the question. Although many soups rely on cream alone for thickening, that doesn’t work for billi bi—the ample fat in cream coats the tongue and completely overpowers the delicate brine of the mussels.
By replacing some of the cream with a smaller volume of egg yolks, which have more thickening power than cream, you can achieve that same luxurious body without the flavor-muting effect. But I needed to find a way to incorporate them into the soup without so much risk of curdling.
Stumped, I paged through other billi bi recipes for inspiration. That’s when I stumbled upon Claiborne’s own billi bi recipe in The Best of Craig Claiborne (1999), which contained an extra step: making a beurre manié, a butter and flour paste that’s whisked bit by bit into the soup to thicken it.
Mussels 101
Mussels may seem intimidating if you haven’t cooked with them before, but they’re actually one of the simplest kinds of seafood to shop for and prepare. Here’s everything you need to know about getting mussels from the fishmonger’s counter to your bowl.
3 Reasons Why We Love Mussels
They’re sustainable. According to the Monterey Bay Seafood Watch, 94 percent of all mussels consumed by humans are farmed—and mussel farming is a sustainable practice. Mussels feed only on organic matter found in the water, and filter feeding by mussels can improve water quality by reducing nitrogen and phosphorous levels.
They’re very economical. Because they feed on naturally occurring nutrients in the water, mussels are less costly to cultivate than other forms of farmed seafood, and that savings is passed on to the consumer.
They require minimal cleaning. Because most mussels are farmed, commonly grown on ropes suspended from rafts that float on the ocean’s surface, they contain less grit than shellfish that live on the ocean floor. They’re also sold thoroughly scrubbed.
I tried it and discovered the underlying genius in this approach: The starch and fat in the beurre manié dispersed smoothly throughout the soup and interfered with the proteins in the yolks linking up and curdling—which meant I could successfully bring the soup to almost 180 degrees, an ideal serving temperature.
I wondered, though, if a roux, a cooked butter and flour paste, would be an easier route to the same result. I could build the roux directly in the pot rather than making a separate beurre manié and adding it piece by piece.
I steamed a final round of mussels and aromatics, shucked the shellfish, and strained the broth. I added butter to the empty pot, heated it until it foamed, and then stirred in the flour to make a roux.
Once it was golden, I whisked in the broth and watched as the mixture started to thicken as it simmered.
Mussel Varieties: The two main varieties of mussels you’ll see at the store are the Atlantic blue mussel and the Pacific green-lipped (also called New Zealand) mussel. These types are interchangeable in cooking, though the green-lipped mussels can be slightly chewier.
Shopping: Like all unshucked bivalves, mussels are sold alive, most commonly in net bags holding 2 pounds. They should smell fresh and briny, never sour or sulfurous, and if their shells are slightly open, they should close tightly when tapped (any that don’t are dead and should be discarded, as should any with cracked or broken shells).
Storage: Mussels are best cooked soon after purchase, but you may refrigerate them for up to three days. As soon as you bring them home, place them in a colander draped with a damp towel and store them in the refrigerator.
Prep: When you’re ready to cook, tap all of your mussels again to confirm they’re still alive if you’ve stored them for longer than a day. Scrub their shells with a stiff brush under cold running water.
Debearding: Some mussels may still have small beards, the tough threads that attach the mussels to the substrate upon which they live. The beards should be removed, but do not pull them out until just before cooking, as doing so can kill the mussel.
Next came the liaison. I added a cup of the hot broth to a mixture of cream and egg yolks to temper it, then poured the liaison into the pot.
As I stirred, the billi bi took on its signature luxe texture—even as the temperature climbed.
Once the soup had reached 180 degrees, it was ready to serve. I divided the plump mussels among several bowls, poured the creamy bisque over them, and sprinkled each bowl with chives.
As I tasted my first spoonful, I knew I had it right—the soup was rich, briny, and perfectly silky-smooth.
Liaison + Roux = A Silky Soup
Adding a liaison, a mixture of egg yolks and cream, is a French technique for enriching and thickening soups and sauces.
As the liquid and liaison heat, proteins in the yolks unfold and bond together into long tangled strands that, along with the fat in the cream, interfere with the movement of water molecules so that the liquid thickens.
But soups made with a liaison can be tricky: If heated above 165 degrees, the proteins in the egg yolks can bond tightly and form curds that mar the smooth texture.
To make our recipe less finicky, we add another element that interferes with the coagulation of the eggs: a roux made with butter and flour.
Like the fat molecules in the cream, the butter and the starch get in the way of the egg proteins, preventing them from joining into curds and enabling the cook to heat the soup more without fear of ruining its texture.
