I’ve often been asked by my students how to make a perfect Béarnaise sauce for steak, grilled chicken and fish. They find it difficult to make because they get confused with the process since Béarnaise sauce is closely related to hollandaise, which is used for poached fish and vegetables, and made with warm egg yolks mixed with lemon juice and warm butter to form a creamy sauce.
The difference is that Béarnaise sauce is more intense in flavor, with more spices. Traditionally, the first rule is to warm the eggs with lemon juice or vinegar using very low heat, making sure the egg does not curdle. Curdled eggs will form lumps and will not mix well with the butter. The amount of butter must not exceed the amount the yolks can absorb, with the ratio being one large yolk to six tablespoons or one-third cup butter.
Next is to melt butter over low heat, ensuring that it does not darken in color. Slowly, add a little at a time the butter to the egg mixture, allowing the eggs to combine or emulsify together, giving it time to thicken. Once the sauce is thick, get another pan and add the tarragon, shallots, pepper, white wine, and reduce in medium heat for three minutes. Add to the sauce and mix well.
Sounds complex? Fortunately, in one of my lessons at Moulin de Mougins, the famed Cannes restaurant, I learned the modern and easy method. Chef Eric explained that you simply add the egg yolks in a blender and pulse for 10 seconds. Then add hot butter a little at a time (two tablespoons in five-second intervals) until thick. Add the tarragon mixture (previously reduced in medium heat for three minutes) and pulse for 15 seconds. Place on a sauceboat and serve right away. If you are afraid to melt the butter in the pan, just melt it in the microwave on high for one minute. A hand mixer may also be used but make sure you use a metal or glass bowl as plastic bowls make the mixture oily. In case the sauce curdles, get another bowl and combine one egg yolk and one-fourth teaspoon mustard. Slowly, add previous sauce and mix until smooth. For variety, tomato paste can be added. Fresh tarragon leaves may be purchased in the supermarket, as well as the bottled, dried version.