Using handheld electric mixer, beat sugar, egg
yolks, corn syrup,
and amaretto in large metal bowl to blend. Place bowl over saucepan
of simmering water (do not allow bottom of bowl to touch water). Beat
until candy thermometer registers 160F and parfait base is thick and
billowy, about 8 minutes. Remove bowl from over water. Continue to
beat parfait base until cool, about 7 minutes. Fold in 1/2 cup almonds.
Beat cream and vanilla in another large bowl until
soft peaks form.
Fold cream into cool parfait base in 3 additions. Transfer parfait
to 13x9x2-inch glass baking dish. Cover and freeze until firm, at
least 4 hours and up to 2 days. Scoop parfait into goblets. Sprinkle
with chocolate and 3 tablespoons almonds.