Preheat the oven to 350 F. Process the cookies and nuts until they are finely ground. Mix with the melted butter and sugar until the mixture is like wet sand (it should hold together when you grab some, but not leave an over oily residue).

Press the wet crumbs into the bottom and up the sides of a 10” tart pan. Use a measuring cup or bottom of a glass to pack it in tightly.

Now lay a sheet of parchment over it and add a smaller cake pan (if you have it, this step isn’t hugely necessary but sometimes it helps keep it all packed in tight). Bake the crust for about 12 minutes. Take it out and let it cool fully.

Add the hazelnuts to a food processor and pulse until chopped finely. It’s fine if it’s uneven and there are bigger and smaller bits.

Bear in mind this is a slightly thin layer of ganache (especially in a 10 inch pan) so increase it by 50% if you want a thick layer.

Chop all of the chocolate very very finely. If you have some bigger bits of chocolate they should be milk chocolate, it’ll melt faster so it’s not as big of an issue. The dark chocolate bits should be no bigger than the size of a black bean. Add it all to a heatproof bowl.

Warm the heavy cream in a pot until it bubbles at the sides and is hot to touch. Pour it over the chocolate and give it a quick stir then leave it for a full minute to begin melting.

Stir until it’s smooth, then add the nuts and stir. Pour the ganache into the cooled shell.

The tart will now keep for a full week in the fridge.

To make the hazelnut butter: toast the nuts on a rimmed baking sheet for 10 minutes at 350 F. While still warm, set them in a food processor and process on high until soupy: this will take 10-15 minutes, stopping and starting the machine to scrape down the bowl. The nuts will turn into tiny bits at first, then chunky, then smooth, and as you keep processing it will turn into a runny paste. Let the paste cool before using to make the mousse.

In a bowl press down on the cream cheese with a rubber spatula or the back of a wooden spoon to remove any lumps. Add the sugar, salt vanilla and beat. Add the hazelnut butter and beat until combined.

Pour in the heavy cream and beat (if you are using a stand mixer you can switch to the whisk attachment) until the mixture is light and fluffy, a couple of minutes at most. If it gets grainy and you see the heavy cream separating, add a bit more heavy cream then briefly beating to bring it back together.

Store the tart in the fridge, it’ll keep for 3-4 days once the mousse is on.