Scrape down sides and continue to blend, slowly adding remaining 1/4 cup oil, until a slightly thick sauce forms (it should cling to a spoon). (epicurious.com)
Slowly add the beer to the roux and bring to a boil, constantly stirring until a thick sauce forms, 1 to 2 minutes. (tastingtable.com)
Pour in olive oil and lemon juice until a thick sauce forms. (cookandbemerry.com)