1. Preheat the oven to 325°F (160°C). Wrap a 9 inch (23cm) springform tin with aluminum foil (make sure it is sealed tight) and place in a large casserole or pan with a high rim – this will be filled with water later on. Set aside. Make sure all ingredients are at room temperature before start preparing the cake.

 

2. Add the chocolate cookies to a freezer bag and crush with a rolling pin until you get fine crumbs. Melt the butter and add to the freezer bag – mix everything until the crumbs are evenly moist. Transfer to the springform tin and press to the bottom to get one even layer. Set aside.

 

3. Chop the chocolate and melt in a heatproof bowl over a pot with simmering water or in the microwave – mix until smooth and let cool down a bit. Set aside.

 

4. Add the room temperature cream cheese, xylitol (or regular sugar), and cocoa powder to a large bowl and mix on low speed until well combined – about 2-3 minutes. Add the eggs and egg yolk and mix in. Add the heavy cream and vanilla extract and mix until well combined – the mix is pretty liquid right now. While mixing, gradually add the melted chocolate and mix in. The mixture in the bowl should thicken up and get darker. If the temperature difference was high, the chocolate might curdle – in that case continue mixing until the mix looks homogeneous. Pour into the prepared springform tin (on top of the crushed cookie base) and smooth out the top. Place the tin (inside the casserole or pan) in the center of the oven and fill hot water around the springform tin about halfway up the edge. Bake for 65-70 minutes or until the edges of the cheesecake are set but the center is still a bit wiggly. Take out of the oven, remove from the water bath, strip off the aluminum foil, and place on a wire rack. Run with a sharp knife around the edges of the cake to loosen it from the tin and let cool down completely, then place in the fridge for at least 6 hours or overnight. Remove from the tin before decorating.

 

5. For the chocolate ganache chop the chocolate and place in a heatproof bowl. Set aside. Add the heavy cream to a small saucepan and heat up until small bubbles appear. Pour over the chopped chocolate and let sit for 2-3 minutes, then mix until smooth. Add the butter in small pieces and mix until smooth. Set aside and let cool down to room temperature. As soon as the ganache has cooled and thickened (takes some time), pour about 3/4 of the ganache over the cheesecake and let it drip down the sides. Place the cheesecake and the rest of the ganache in the fridge. When the remaining ganache has set, whip it briefly with a hand mixer and fill into a piping bag. Decorate the cake with a few dollops of ganache, chocolate pieces, and chocolate shavings. Keep cake leftovers in the refrigerator.