In a mixing bowl, combine the ricotta cheese, mascarpone cheese, powdered sugar, vanilla extract, and cinnamon. Mix until smooth and creamy. Gently fold in the mini chocolate chips. Set aside.
Lay 5 sheets of phyllo pastry on a clean surface, brushing each sheet with melted butter before adding the next one. Repeat with 5 more sheets, creating a stack of 10 sheets total.
Cut the layered phyllo pastry into squares (about 4x4 inches) and place them in a greased baking pan, overlapping slightly if necessary.
Bake the phyllo squares in the preheated oven for about 10-12 minutes or until they are golden brown and crispy. Remove from the oven and let them cool.
Once the phyllo squares have cooled, spread a generous layer of the ricotta filling on each square.
Top with additional mini chocolate chips and sprinkle chopped pistachios over the filling for added crunch.
For garnishing, add a fresh mint leaf on top of each square.
Slice into squares for serving and enjoy your delicious cannoli squares!