Preheat oven to 350°. Stir together first 3 ingredients. Firmly press on bottom and up sides of a 9-inch tart pan. Bake 8 to 9 minutes or until fragrant. Cool on a wire rack 30 minutes.
Bring cream to a boil in a 3-qt. saucepan over medium-high heat.
Process chocolate in a food processor or blender until finely ground. With processor running, pour hot cream and vanilla through food chute in a slow, steady stream, processing until smooth, stopping to scrape down sides as needed.
Pour mixture into cooled crust. Chill, uncovered, 3 hours. Garnish, if desired.