Hazelnut Crust

1. Preheat oven to 150°C (300°F), non-fan-assisted. Spread the chopped hazelnuts on a small baking tray lined with parchment paper or a silicone baking mat.
2. Toast the hazelnuts for about 6-10 minutes, until darkened and they smell deliciously nutty. Cool for about five minutes in the pan.
3. Whilst the nuts are toasting, grease a 9-inch (24 cm) round tart pan and sprinkle some flour into it. Don’t forget to grease and flour the sides too! There should be a very fine layer of flour covering the whole pan, so the crust comes out without sticking.
4. Reserve 30 g of the toasted hazelnuts. Put the remaining 100 g in a food processor together with the flour, sugar, and salt. Pulse until the mixture resembles coarse, dry sand.
5. Cut the butter into walnut-sized cubes, and add into the food processor. Pulse a few times, carefully, until pea-sized dough-chunks form. Immediately stop pulsing.
6. Next, pour in 2-3 tablespoons of ice-cold water. Start with one tablespoon, pulse 2-3 times, and add another tablespoon. If the dough doesn’t stick together yet, add some more water.
   Go sparingly, as the hazelnut crust shouldn’t be too wet!
7. When big chunks remain, take the dough out of the food processor, and knead a few times by hand. Carefully press the dough into the prepared tart pan, making sure the crust is as even and as tight as possible. Use the bottom of a measuring cup coated in flour and/or floured hands to press the dough down evenly. Prick the crust with a fork a couple of times.
8. Turn the oven up to 175°C (350°F). Next, scrunch up a sheet of parchment paper, spread it out again, and lay it onto the prepared, unbaked tart crust. Pour pie weights or rice onto the paper.
9. Bake for around 20 minutes, and take the tart out of the oven. Lift out the parchment paper with the pie weights, and bake further for 10-20 minutes until golden brown.
10. Let the crust cool in the tart pan for around 10 minutes, then remove the sides, if using a tart pan with a removeable bottom. (If you are using a glass dish, leave the crust in to cool.)
11. Let cool in the fridge for 30 minutes to an hour, or even overnight, until ready to fill.

Chocolate Nutella Ganache Filling

1. Chop the chocolate and put it into a heatproof bowl. Add in the Nutella.
2. In a medium-sized pot, heat the cream until it starts to boil. Pour into the bowl of chocolate and let stand for 2-4 minutes.
3. Using a spatula, stir until the chocolate Nutella ganache comes together (it takes around 1-2 minutes of stirring until the ganache thickens).
4. As soon as the ganache has come together, pour it into the cooled hazelnut crust, and spread evenly.
5. Sprinkle the remaining hazelnuts on top. Put in fridge until ready to serve (at least 1-2 hours or overnight).
6. Before serving, sprinkle on some flaky sea salt.