Liaison
A liaison is a mixture of egg yolks and heavy cream used to finish soups and sauces, adding richness, a velvety texture and light thickening. It's whisked in at the end of cooking, after being tempered with some of the hot liquid so the yolks don't scramble.
How a liaison works
Egg yolks contain proteins that unfold and link together when heated, forming a loose network that traps liquid and thickens it. Cream adds fat, which coats the yolk proteins and slows them down, making the mixture more forgiving and adding body.
Yolk proteins begin to thicken around 65–70 °C / 149–158 °F and are at their best near 80 °C / 176 °F. Above about 85 °C / 185 °F, they bond too tightly, squeeze out liquid and form curds. The same science governs custard and crème anglaise.
A liaison thickens only slightly. It's mainly for richness and silkiness, not for turning thin liquid into gravy. For real thickening, use a roux, slurry or beurre manié first, then finish with a liaison.
Classic ratio
- 1 part egg yolk : 3 parts heavy cream by volume.
- One large yolk is about 18 g (just over 1 tbsp).
- For about 1 litre (4 cups) of soup or sauce: 2–3 yolks plus 125–175 ml (½–¾ cup) heavy cream (35%).
How to add a liaison
- Whisk yolks and cream together in a bowl.
- Make sure the soup or sauce is hot but not boiling.
- Temper: slowly whisk about a third of the hot liquid into the liaison.
- Pour the warmed mixture back into the pot, stirring constantly.
- Heat gently, without boiling, until slightly thickened, ideally to about 80 °C / 176 °F.
- Serve promptly.
Where you'll see liaisons
- Velouté-based sauces like sauce allemande and sauce suprême.
- Cream soups, such as cream of mushroom or asparagus.
- Blanquette de veau and chicken fricassée.
- Greek avgolemono, which uses egg and lemon instead of cream.
Common mistakes
- Skipping the temper: leaves scrambled flecks.
- Boiling after adding: curdles the sauce.
- Reheating leftovers hard: reheat gently over low heat, stirring.
- Holding too long: a liaison-finished sauce shouldn't sit hot for hours. Serve within about 30 minutes and refrigerate leftovers promptly.
If small curds appear, strain the sauce or blend it briefly; it may smooth out.
Questions
What is the ratio for a liaison?
The classic ratio is 1 part egg yolk to 3 parts heavy cream by volume, for example 1 yolk (about 18 ml) with 60 ml (¼ cup) cream. Roughly 2–3 yolks with 125–175 ml cream enriches about 1 litre of soup or sauce.
Why must you temper a liaison?
Adding cold yolks straight to hot liquid cooks them instantly into flecks. Whisking some hot liquid into the liaison first warms it gradually, so it blends smoothly.
Can you boil a sauce after adding a liaison?
No. Above about 85 °C / 185 °F the yolk proteins tighten and curdle. Heat gently to about 80 °C / 176 °F and serve soon.
Does liaison mean other thickeners too?
In French culinary language, liaison can refer to any binding or thickening agent, including roux and starch. In English kitchens it usually means the egg-yolk-and-cream mixture.