The head chef of the Prince of Joinville had several white-coloured sauces on the go in the kitchen—crème anglaise, chantilly, a butter sauce for glazing and a béchamel—all waiting to be finished. Overwhelmed, he asked his apprentice to add butter to the béchamel.
But the apprentice mistakenly added the butter to the crème anglaise, whisked it and let it cool and voilà! crème au beurre was born.
A proper crème au beurre is not as easy to make (or as sweet) as American or ‘mock’ butter cream: sugar and water are heated to the soft ball stage (petit boulé, 120 °C/248 °F) and slowly added to whipped egg yolks and beaten until the mixture cools, before adding beurre pommade (butter beaten to a pomade-like consistancy) and silky smooth. Add any flavouring, chill, and it’s ready to fill a cake.
Another name for it is pâte à bombe.
Image by Whitney