
Heat 3/4 cup cream in a 1-quart heavy saucepan
until hot. Whisk
together yolks, sugar, and a pinch of salt in a
metal bowl until
combined well, then add hot cream in a slow stream,
whisking until
combined. Transfer mixture to saucepan and cook
over moderately low
heat, stirring constantly, until it registers 160F
on thermometer.
Pour custard through a fine-mesh sieve into a bowl
and stir in
vanilla.
Melt chocolate in a double boiler or a metal bowl
set over a pan of
simmering water (or in a glass bowl in a microwave
at 50 percent
power 3 to 5 minutes), stirring frequently. Whisk
custard into
chocolate until smooth, then cool.
Beat remaining 1 1/4 cups cream in a bowl with
an electric mixer
until it just holds stiff peaks. Whisk one fourth
of cream into
chocolate custard to lighten, then fold in remaining
cream gently but
thoroughly.
Spoon mousse into 8 (6-ounce) stemmed glasses or
ramekins and chill,
covered, at least 6 hours. Let stand at room temperature
about 20
minutes before serving.
