Combine first 7 ingredients in a heavy nonaluminum saucepan. Cook, whisking constantly, over medium heat 8 to 10 minutes or until butter melts and sugar dissolves.
Gradually whisk about one-fourth of hot sugar syrup into beaten eggs; add to remaining hot syrup, whisking constantly. Reduce heat to medium-low; cook 12 to 15 minutes, stirring gently, or until curd thickens and coats a spoon; let cool. Cover and chill overnight.