Heat 3/4 c. heavy cream to a boil.
Pour over chocolate in heatproof bowl; stir until smooth.
Pour into graham cracker crusts; chill 6 hours.
For whipped cream:
Combine 1 c. heavy cream, sugar, orange zest, and vanilla in a large, chilled mixing bowl.
Beat until soft peaks form.
Top each tart with whipped cream and a fresh raspberry.
*Allow to rest at room temperature at least 15 minutes before serving.