1. To prepare Rum-Raisin Mascarpone, soak raisins in a mixture of the granulated sugar, rum, and lemon juice. Muddle (squash) raisins with a wooden spoon to help them soak and rehydrate a little. Set aside while you prepare the rice pudding.
2. Put milk, butter, brown sugar, cinnamon, vanilla bean contents, rice, and salt into a large saucepan. Bring to a simmer over medium heat; stirring constantly. Simmer Arborio rice for 20 to 22 minutes, until tender, yet firm (al dente). (The rice mixture should have slightly more liquid than regular risotto.) Remove from heat; stir in creme fraiche.
3. Strain the liquid from the raisins; reserve liquid. Combine mascarpone and cream and whisk until light and creamy in a large bowl. Swirl in the strained raisins and drizzle a little of the soaking liquid over top. Garnish rice pudding with lemon zest. Top rice pudding with a generous spoonful of Rum-Raisin Mascarpone. Serve pudding with additional Rum-Raisin Mascarpone on the side.