For the Crumble:

1. Preheat oven to 350°F. Place the cookies and hazelnuts in a food processor and pulse until fine crumbs form. With the machine running, stream in the melted butter and add a pinch of sea salt.
2. Spread the crumbs on a parchment-lined baking sheet and bake for 10 minutes. Cool completely.

For the Mousse:

1. Whip the cream in the bowl of a stand mixer until stiff peaks form. Add in the vanilla extract and 2 tablespoons of the sugar and beat to incorporate. Transfer the whipped cream to another bowl.
2. Add the cream cheese, remaining sugar, and nutella to the bowl of the stand mixer and whip until completely combined and smooth. Whisk in the milk and a pinch of salt.
3. Using a spatula, fold the whipped cream into the nutella mixture.

To Assemble:

1. Add a few tablespoons of the crumble to the bottom of your serving dishes (I like serving these as individual parfaits, but you could definitely assemble this as one large parfait in one dish). Add a layer of the mousse, about ¼ cup. Repeat the layers a couple times (depending on the size and shape of your serving dishes) and garnish the last layer of mousse with the crumble. Refrigerate until ready to serve.