Line a large strainer with cheese cloth and strain the ricotta cheese for a couple of hours in the refrigerator.
Add the ricotta cheese to the bowl of a food processor. Sift in the powder sugar and process together for about 45 seconds until incorporated and fluffy.
Alternately you can add the ricotta cheese and sugar to a bowl and using a hand held blender with the whisk attachments beat together until combined and fluffy.
Serve as is with the chocolate pizzelle cookies or stuff inside freshly made cannoli shells.
To make the chocolate pizzelle: prepare a double boiler on the stove top.
Break the chocolate into chunks and add them to the double boiler bowl. Allow it to gently melt in the bowl over the steam. As soon as the chocolate is smooth turn off the flame and stir in the butter until melted. It will melt from the heat of the chocolate.
Take each pizzelle cookie and dip it half way in the melted chocolate. Place them a parchment paper lined baking sheet and sprinkle with some chopped pistachios. Place in the refrigerator for a few minutes to allow them to cool off and for the chocolate to set.
Serve the chocolate pizzelle with the whipped cannoli filling as a dip or simply spooned on top.