Whisk yolks and sugar in top of double boiler over simmering water, stirring constantly, until the mixture is thick and lemony, about 5 minutes. Add marsala; keep whisking until mixture thickens enough to coat back of spoon, about 2 minutes.
Transfer to large bowl. Let cool, whisking occasionally.
Meanwhile, beat cream until stiff peaks form. Gently fold whipped cream into egg mixture. Cover; refrigerate 30 minutes.
Fold in raspberries. Refrigerate 1 hour or overnight. Garnish with more berries if desired.
