Beat cream in a large bowl until foamy. Gradually add sugar, continuing to beat until stiff peaks form. Lift your beater or whisk straight up: the cream should form a sharp peak. Add sweetened condensed milk and egg yolks; beat until well mixed. Slowly beat sweet potatoes into cream mixture until well blended. Stir in cinnamon.

Crumble graham cracker crusts into the sweet potato mixture; pour into an ice cream maker and freeze according to manufacturer's directions until it reaches 'soft-serve' consistency, about 6 hours. Transfer ice cream to a lidded plastic container; cover surface with plastic wrap and seal. For best results, ice cream should ripen in the freezer for at least 2 hours or overnight.