Beat cream and 1/2 c.powdered sugar to stiff peaks.
In another bowl, combine strained ricotta, mascarpone, 1/4c. powdered sugar, and vanilla.
Fold in whipped cream.
Taste for sweetness-you can add the other 1/4c. powdered sugar if you want it sweeter.
Refrigerate until ready to fill cannoli, at least 1 hour.