How to Make It
In a microwave-safe bowl, sprinkle the gelatin over 2 tablespoons of water and let stand until softened, 3 minutes. Microwave at high power for 10 seconds, until melted. In a microwave-safe measuring cup, microwave the reserved brown butter solids with the milk, sugar, 1/8 teaspoon of the cinnamon and a pinch of salt until warm. Whisk in the gelatin and refrigerate until set.
In a bowl, whisk 3/4 cup of the heavy cream and sour cream to soft peaks. Whisk the custard to loosen it, then fold into the whipped cream. Pour the custard into the Cinnamon Toast Crumb Crust; refrigerate for 30 minutes.
In a microwave-safe bowl, melt the white chocolate and butter. Add the mashed sweet potatoes, the remaining 2 tablespoons of heavy cream and 1/8 teaspoon of cinnamon and a pinch of salt; whisk until smooth. Transfer the sweet potato ganache to a pastry bag fitted with a 1/2-inch plain tip and refrigerate until chilled slightly, 15 minutes. Pipe 1-inch mounds around the edge of the pie. Refrigerate until the ganache is set, 10 minutes.
Pour the cranberry puree over the pie and spread it evenly with the back of a spoon. Refrigerate until set, at least 30 minutes. Cut the pie into wedges and serve.