Purée ricotta, cocoa powder and coffee in a blender until smooth. Transfer to a large bowl; set aside.
In a separate bowl, using an electric mixer, beat the cream until thick. Add the powdered sugar and continue to beat until the cream holds stiff peaks.
Fold in cream into the ricotta mixture in 3 stages. Spoon the mousse into serving bowls and refrigerate for 1 hour.
Garnish with chocolate shavings and mint and serve.