Bring large saucepan filled halfway with water to a boil; reduce heat to simmer.
In large metal bowl, whisk together yolks, sugar and liqueur until blended. Place bowl over saucepan of simmering water. With mixer on medium speed, beat yolk mixture until very thick and instant-read thermometer registers 140 degrees F, about 7 minutes; cook for another 3 minutes, beating, and keeping the temperature at 140 degrees F.
Scrape mixture into clean bowl. Place bowl in larger bowl filled with ice and water. Let cool completely, stirring occasionally with rubber spatula.
In medium bowl, beat heavy cream until it just holds stiff peaks. Gently fold whipped cream into yolk mixture. Cover and refrigerate (can be prepared 6 hours ahead).
To serve, divide berries into 8 serving dishes. Spoon about 1/4 cup sauce over each. Makes 8 servings.