What's better than one kind of chocolate? Three--dark and white chocolate, plus crunchy chocolate chip cookie crumbles.
In three separate medium bowls, place 4 oz. dark chocolate, 2 ounces dark chocolate, and white chocolate.
In a small saucepan heat 1 cup cream over medium until just simmering.
Pour 1/2 cup hot cream over the 4 ounces dark chocolate, 1/3 cup hot cream over the 2 ounces dark chocolate, and the remaining hot cream over white chocolate. Let stand 5 minutes without stirring. Stir each until smooth. If necessary to melt, place each bowl in a slightly larger bowl of hot water and stir until smooth. Stir vanilla into white chocolate ganache. (It may be softer than dark chocolate mixtures.) Stir espresso into the darker chocolate ganache. (The one with 4 oz. dark chocolate.)
In a large bowl beat the remaining 2 cups cream with a mixer on medium until soft peaks form. Divide whipped cream evenly among the three bowls; fold into each until no streaks remain.
Spoon or pipe half the espresso chocolate mixture into the bottom of ten to twelve 3- to 4-ounce glasses. Tap glasses lightly to even layers. Crush two cookies; break remaining into pieces and set aside. Sprinkle crushed cookies over chocolate in glasses. Top with remaining espresso chocolate mixture, white chocolate mixture, then light chocolate mixture, tapping glasses lightly between layers. Chill at least 2 hours or until set. Sprinkle each mousse with cocoa powder. Top with broken cookie pieces. Makes 10 to 12.
The mousse is best served cold, straight from the refrigerator. Choose good-quality white chocolate bars. White chocolate chips don't have enough cocoa butter.