Stir in butter and cook over moderately low heat, whisking frequently, until curd is thick enough to hold marks of whisk and first bubble appears on surface, about 6 minutes. (epicurious.com)
Source: AllianzGI; Datastream; Peter Garber (1990), «Famous First Bubbles»; Federal Reserve Economic Data; Robert J. Shiller (2000), Irrational Exuberance; Earl Thompson (2007), «The Tulipmania: Fact or Artifact?» (allianzgi.com)
Back in 1842, pilsners first bubbled up in Bohemia's Plzeň (a.k.a. Pilsen, now in the Czech Republic), the clear, golden, generously hopped liquid was a night - day difference from its dark, often murky contemporaries. (bonappetit.com)