Melt the butter.

The butter is clarified by gently heating it in a heavy-bottomed pot over low heat. Once melted, it should be poured into a new container (preferably a small jug), and the white residue should be discarded.

The burner should be set to the lowest or next lowest heat setting. Besides consistent temperatures, whisking, whisking, and whisking are key words you should remember.

Whisk the egg yolks with vinegar and mustard over very low heat. Continue whisking until it foams and thickens slightly.

Add a small amount of butter while whisking vigorously.

Continue with a little more butter and keep whisking.

You can gradually add more and more butter while whisking. The more butter, the thicker your sauce will become.

When the sauce has reached the desired thickness, season it with salt, pepper, cayenne pepper, and optionally lemon juice.

Remember that the sauce should never exceed 63 degrees Celsius (145 degrees Fahrenheit), or it will separate. A true sauce should not be hot; it should be warm.

Serve immediately.