Preheat the oven to 325°F (163°C). Line a standard muffin tin with paper cupcake liners. In a medium mixing bowl, combine the graham cracker crumbs and the granulated sugar. Add the melted butter and stir until the mixture is evenly moistened. Divide the crumb mixture evenly among the cupcake liners, pressing it firmly into the bottom of each liner using the back of a spoon or the bottom of a small glass. Bake the crusts for 5 minutes. Remove from the oven and allow to cool while preparing the filling.

In a large mixing bowl, beat the softened cream cheese using an electric mixer until smooth and free of lumps. Add the granulated sugar and continue beating until fully incorporated. Add the eggs one at a time, mixing well after each addition. Incorporate the vanilla extract. Stir in the melted white chocolate, ensuring it has cooled slightly before adding. Finally, add the sour cream and blend until the batter is smooth and homogeneous.

Spoon the cheesecake filling over the cooled crusts, filling each liner approximately three-quarters full. Place small spoonfuls of the blueberry jam on top of the filling in each liner. Using a toothpick or skewer, gently swirl the jam into the batter to create a marbled effect. Distribute a few fresh blueberries evenly over the top of each cupcake.

Bake the assembled cupcakes in the preheated oven for 20 to 25 minutes, or until the edges appear set and the centers exhibit a slight jiggle. Avoid over-baking, as this may cause the cheesecake to crack. The cupcakes will continue to set as they cool.

Allow the cupcakes to cool to room temperature within the muffin tin. Once cooled, transfer the cupcakes to the refrigerator and chill for a minimum of 2 hours to ensure the cheesecake filling sets completely and achieves the desired texture.

After chilling, remove the cupcakes from the muffin tin and carefully peel off the paper liners. Serve as is, or garnish with additional blueberry jam, a drizzle of melted white chocolate, or a dollop of whipped cream for an elegant presentation.