Melt chocolate over a double boiler. Let cool slightly.
In a large mixing bowl, whisk together sour cream and sugar.
Add melted white chocolate in 3 parts, whisking well after each addition.
Add vanilla and egg and whisk well.
Add flour and whisk until combined.
Pour the filling over the crust.
Place tablespoons of cranberry jam over the filling, spreading gently.
Crumble the reserved topping in your hands and sprinkle over the jam.
Bake the bars for 30 to 35 minutes, or until golden brown on top. It can slightly jiggle in the middle. The bars will set as they cool.
Cool to room temperature.
Let set in the fridge for at least 30 minutes if you want to have more even slices.