For the cake: In the mixer with the paddle attachment, cream the almond paste, egg, powdered sugar and vanilla paste and mix until creamy with no lumps. Then add the egg yolks one at a time, mixing well after each addition.
Change the paddle to the whisk, and whisk for another 6-8 minutes. Fold in the flour, then the melted butter.
Whisk the egg whites and sugar together to a soft peak making a meringue. Lastly fold in the meringue.
Spread on a cookie sheet in a very thin layer and bake at 375 degrees F for about ten minutes.
For the mousse: Cook the sugar and water to a glucose/syrup consistency. Place the egg yolks in the mixer and whisk until the color is pale and the consistency is thick. Then add the sugar/water syrup slowly and whisk until room temperature.
Warm the pumpkin puree with the vanilla paste and pumpkin spice. Whisk in the gelatin and mix well.
Bring the heavy cream to a soft peak by whisking it in a mixer. Fold the puree mixture into the egg yolk mixture and then fold in the whisked heavy cream. Pour the batter onto the biscuit cake.
For the streusel: In the food processor combine all of the ingredients together and mix until it becomes a corn meal consistency.
Spread the mixture over a silpat and bake at 300 degrees F until crispy and dry, about fifteen minutes. Chill and break into pieces.
For Serving: Divide the mousse pie into eight squares and top with the streusel. This dessert can be served with an optional scoop of vanilla ice cream.