Spread the pumpkin puree in a thin layer on a large baking sheet. Bake at 350℉ (177℃) for 25 to 30 minutes until deepened in color and the pumpkin has reduced to about 2 cups (500g). If you have more pumpkin than this, continue roasting to remove more of the moisture from the pumpkin (different brands tend to have slightly different amounts of water). Set aside to cool completely.
2 (15-ounce) cans pumpkin puree
Combine the cream, butter, and corn syrup in a small saucepan over medium heat just until it comes to a boil. Remove from the heat and pour the hot liquid over the chopped white chocolate in a large heat-safe bowl. Let this sit for 1 minute without stirring while the white chocolate melts.
1 1/4 cups (277g) heavy cream, 1/3 cup (129g) corn syrup, 5 Tablespoons (71g) salted butter, 16 ounces (443g) chopped white chocolate
Add the roasted pumpkin, cinnamon, cardamom, allspice, ginger, cloves, and salt to the white chocolate mixture. Blend well using an immersion blender or electric mixer until everything is completely combined and smooth.
2 teaspoons ground cinnamon, 1 teaspoon ground cardamom, 1/2 teaspoon ground allspice, 1/2 teaspoon ground ginger, Pinch of ground cloves, 1/4 teaspoon kosher salt
Pour the white chocolate pumpkin ganache mixture over the set caramel layer in the pie crust, spreading it all the way to the edges of the pie to completely cover the caramel. The pie dish will be very full. Cover with plastic wrap and transfer the pie to the fridge to chill overnight until fully set.