Line the bottom of a 7 inch springform pan with baking paper that's bigger in diameter than the pan. Then put the ring on top.
Using a food processor ground your cookies. In a separate bowl, combine them with the melted butter using a spoon. Press the mixture into the bottom, making sure it's level. Put in the fridge for approx. 20 min to harden.
for edible cookie dough
Toast the flour for about 4-5 minutes on a medium to high heat, stirring all the time. It will change its colour a little bit. Leave it to cool before using.
In a medium sized bowl, using a hand mixer mix together butter and sugars until lighter and fluffier. (approx. 3 minutes) Add yogurt, vanilla extract and salt and mix until everything is combined.
Add cooled, toasted flour and mix just until everything is incorporated. In the end add finely chopped chocolate and mix until everything is combined.
The dough will be a little sticky. Cover the bowl in cling film and leave it in the fridge for about 20-30 min to harden a bit.
for nutella cheesecake filling
Melt chocolate over a bain marie or in a microwave (using 30 sec intervals so it doesn't burn) and leave it to cool, but it should still remain melted.
In a medium sized bowl, using a hand mixer, mix together cream cheese, mascarpone and vanilla extract. Add sifted powdered sugar and mix until combined. Next, add both the nutella and melted chocolate and mix until everything is incorporated and there are no white streaks left.
In a separate bowl, beat heavy cream until it reaches soft peaks. Then gradually fold it into the nutella cream cheese mixture using a silicone spatula.
Chocolate sauce
Place finely chopped dark chocolate in a medium sized bowl and pour over it almost boiling heavy cream. Cover it with a plate and leave it for 2-3 minutes. Stir with a silicone spatula to combine.
Assembly:
Once your buttery biscuit base is cooled, it's time to add the cookie dough layer on top.
Grab the bowl with cookie dough from the fridge, it should be a little firmer now. Get your latex gloves on and sprinkle the cookie dough in small chunks all over the base. Then press it down with your fingers to make one even layer. Put in the fridge for 15-20 minutes before putting on the filling.
After the cookie dough layer has cooled a bit, fill the pan with prepared filling. Use a small offset spatula to make the top even and smooth.
Put the cheesecake in the fridge for at least 4 hours to firm up a bit, before cutting into it and decorating it with leftover cookie dough and chocolate sauce.
Notes
You can use an 8 inch springform pan as well, just make sure to add a little bit more cookies for a cookie crust. (125 g + 63 g butter)