Melt chocolate over simmering water of a water bath.
Whip egg yolks with 1/3 cup powdered sugar until pale and airy, place whipped yolks in medium sized bowl.
Add warm melted chocolate and fold until just mixed. Wash bowl and wipe thoroughly.
Dissolve 1/3 cup granulated sugar and 1/4 cup water in small pot, bring to a boil, cook to 230 degrees on a candy thermometer.
While sugar is boiling slowly whip whites to soft peak.
When sugar is ready, slowly pour into whites while beating at a medium speed in a steady stream.
Continue to whip until stiff peaks form.
Remove whites, spoon whites on top of yolks but do not fold in.
Whip cream and 1/3 cup powdered sugar until medium stiff peak, now fold in whites until just mixed. Add cream and fold until incorporated, do not over fold.
Store in refrigerator until ready to use (should be used as soon as possible).
Melt chocolate hot, over double broiler (do not burn chocolate), heat until it is warm to the touch.
Whip cream until very soft peaks form (lines show in slightly whipped cream).
Very, very quickly add chocolate to cream and fold in, mixture may look broken but keep folding until everything is smooth, but do not overmix.
Place in bowl, cover and refrigerate until set.
To serve, place the two mousses in composition to contrast each other. Garnish with berries and crisp a cookie, if desired