Preheat oven to 425°. Unroll 3 piecrusts, and stack on top of one another. Cut piecrust stack 10 times using a 3-inch round cutter, making 30 rounds. Press rounds into bottoms of ungreased muffin cups. (Dough will come halfway up sides, forming a cup.) Flute edges with a fork, if desired.
Bake rounds at 425° for 8 to 10 minutes or until golden. Let cool on a wire rack 10 minutes. Remove from pans to wire racks, and let cool completely (about 20 minutes).
Meanwhile, stir together chocolate and cream in a 3 1/2-qt. heavy saucepan over low heat, and cook, stirring constantly, 4 to 5 minutes or until chocolate is melted and mixture is smooth. Remove from heat; stir in vanilla and salt. Let cool 30 minutes.
Pour 1 Tbsp. chocolate mixture into each piecrust. Cover and chill 1 to 24 hours. Top each with a dollop of sweetened whipped cream. Garnish, if desired.