Melt the white chocolate in a bowl set over simmering water until smooth. Add the pumpkin puree and gently mix to combine. Set aside to cool.
Make sure that your puree is at room tempertaure. (If it is cold from the fridge it will cause the white chocolate to firm up and you will not have a smooth mixture.)
In a small sauce pan whisk together the egg yolks, sugar, cinnamon and ginger until smooth. Gradually whisk in the 6 tablespoons of cream.
Place the pan over medium low heat and stir with a spatula, occassionally scraping the bottom and sides of the pan, until the mixture thickens.
You can also place the mixture in a bowl over a double boiler and heat until thickened. (This will take much longer to thicken the mixture, but it will prevent the mixture from burning)
Take the thickened egg/cream mixture and pass it through a wire mesh strainer into the pumpkin/white chocolate. Mix with a spatula until combined
Whip the heavy cream to between medium and stiff peaks.
Make sure that the pumpkin mixture is cool to the touch then fold in the whipped cream. (If the pumpkin mixture is still warm, place in the fridge for a few minutes until it is cool to the touch)
Pour the mouse into the prepared crust and smooth the top with an offset spatula.
Place in the refrigerator and let set overnight.