Put the chocolate in a microwave-safe bowl. Microwave about 2 minutes, stirring every 30 seconds, until melted. Put the pistachios in another bowl. Dip both ends of each cannoli shell in the chocolate, then into the pistachios. Arrange on a baking sheet and refrigerate.
Beat the ricotta, confectioners' sugar, tangerine zest and juice, and the cinnamon in a bowl with a mixer until fluffy, about 10 minutes. Add the heavy cream and continue to beat until creamy, 1 to 2 more minutes. Cover and refrigerate at least 30 minutes.
Transfer the filling to a pastry bag and pipe into the prepared shells from both ends. Dust with confectioners' sugar before serving.
Photograph by Tina Rupp
Recipe courtesy of Food Network Magazine