Preheat your oven to 150°C (300°F). Melt the butter and crush the ginger snaps into fine crumbs—you want a mixture similar to wet sand. Combine the crumbs with the melted butter and press firmly into the bottom of a springform pan, creating an even layer. Grease the sides of the pan generously with butter or cooking spray to prevent sticking, then refrigerate the crust while you prepare the filling.
In a large bowl, combine the mascarpone and fromage frais, whisking until smooth and well blended. Add the eggs one at a time, mixing gently after each addition to avoid overbeating. Stir in 3 tablespoons of sugar and the vanilla extract. The mixture should be creamy and homogeneous. I like to use a whisk for this step rather than an electric mixer—it gives me better control and keeps too much air from incorporating, which can cause cracking during baking.
Melt the white chocolate gently over low heat or in short intervals in the microwave, stirring frequently to avoid scorching. Once melted and slightly cooled, fold it into the cheese mixture from Step 2 until fully incorporated. In a separate bowl, toss the 7.05 oz of rhubarb pieces with 1 tablespoon of sugar and let them sit for 2 minutes to release their juices. Fold the sugared rhubarb into the chocolate-cheese mixture—the rhubarb will add beautiful flecks and tartness throughout the cake.
Pour the filling mixture from Step 3 into your chilled crust and smooth the top with a spatula. Bake for 1 hour at 150°C (300°F) until the top is set but the center still jiggles very slightly when you gently shake the pan—this indicates the cheesecake will have a creamy, luxurious texture. Turn off the oven and crack the door open slightly, leaving the cheesecake inside for another hour. This gradual cooling prevents the dreaded cracks from temperature shock.
While the cheesecake cools in the oven, heat the 1.75 oz of finely sliced rhubarb with the cranberry juice in a small pot over medium heat, stirring gently until the rhubarb softens and breaks down into a compote, about 5-8 minutes. Once soft, remove from heat and let cool completely. After the cheesecake has rested in the cooling oven, remove it and run a thin knife around the edges to loosen it from the pan. Allow the cheesecake to cool completely to room temperature on the counter, then refrigerate for at least 4 hours or overnight for best flavor and texture development.
Combine the 4.06 oz mascarpone and 2.65 oz fromage frais in a small bowl, mixing until smooth and spreadable. Once the cheesecake is fully chilled, spread this creamy layer evenly across the top. Spoon the cooled rhubarb compote from Step 5 over the top, creating a beautiful tartness contrast to the rich white chocolate. I find that adding white chocolate curls just before serving keeps them crisp and adds an elegant professional touch to the presentation.