Fill two or three small paper pastry bags with the melted chocolate. Cut a small opening in the tip of one, and set the others aside in a warm place.
To stuff the raspberries, hold each berry upside down and pipe chocolate into the interior, then lay the berry on its side on the prepared baking sheet. Refrigerate for 15 minutes.
Pour the cream into the bowl of a stand mixer or a medium mixing bowl. Using the whisk attachment or a hand-held mixer, beat at medium speed until soft peaks form. Beat in the sugar. Spoon the whipped cream into the tart shells. Refrigerate for 15 minutes.
Mound the raspberries into small pyramids in the centers of the tarts, leaving a border of cream around them, and serve.