These are remarkably just like the cannoli I used to buy at my favourite bakery in my home town. The difference between these and Cannoli Siciliani is that they contain chocolate chips instead of candied fruits. I've also found that I prefer grated semi-sweet chocolate over the chips. Especially when I make two-bite cannoli.
I use cannoli shells purchased already made from my local Italian food importer and I make the filling myself from scratch using the following recipe:
Drain 1 kg of ricotta in the refrigerator overnight by placing it in a sieve over a bowl and covering the ricotta with plastic wrap. Be sure it is cold and dry, but not iced. Mix in about 10 tablespoons of sifted confectioner's sugar (to taste). Add a teapoon of vanilla, 1/2 tsp cinnamon and little heavy cream if the mixture becomes too stiff. Mix well with electric mixer until you have a smooth cream. Fold in 1/4 cup chocolate chips. Store in the fridge until ready to serve.
When ready to serve, pipe the ricotta cream into the shells first from one end and then the other. If you like you can garnish each end with a half maraschino cherry.
Dust with some confectioner's sugar and serve!