Whip heavy whipping cream to a medium stiff peak. Set aside.
In a medium bowl, combine cream cheese, confectioners' sugar, vanilla, and lemon zest until combined and fluffy. This works best with an electric mixer. The fluffier you cream this, the lighter your mousse will be.
Fold in 1/3 of the whipped cream, and stir until well incorporated. Don't worry about being too careful with this first addition.
Gently fold in remaining whipped cream in two separate additions. Folding and cutting down through the center until well incorporated.
Refrigerate until ready to serve.
For the crumble
In a food processor, mortal, or plastic bag, add 2-3 cookies and a small handful of freeze dried fruit. Crush until desired consistency, adding more of either to reach the flavor and color desired.
Store in ziplock bag until ready to use.
To assemble
Mousse may be piped or scooped into dish.
Crumble can be used as a crust or sprinkled on top of mousse. See above notes for specific ideas.
Notes
Store mousse in refrigerator for up to 5 days. Crumble can be stored in an airtight bag/container at room temperature until used.