Pour half-and-half into a saucepan and sprinkle gelatin over it. Allow gelatin to bloom for 5 minutes.
Add sugar and stir over medium-low heat until the sugar is dissolved. Add chocolate and stir, over low heat, until the chocolate is melted and the mixture is smooth.
Pour filling into the baked tart or pie shell and refrigerate until set, at least 3 hours. Top with whipped cream and chocolate shavings before serving.