Finely chop the chocolate. Place in a microwave safe bowl and microwave, 30 seconds at a time, stirring after each time until fully melted. Allow to cool at least 20 minutes.
Using either a stand mixer or hand mixer and large bowl, combine 2 ½ cups heavy cream, mascarpone, sugar and vanilla and mix on medium speed until stiff peaks form.
Fold in melted chocolate until fully combined. You will have chocolate shards throughout the cream mixture.
In an 8 in springform pan, completely line the bottom with a layer of chocolate chip cookies, breaking them as needed to fit any small spaces.
Dollop 1 cup of cream on top of the cookies and spread evenly to cover the cookies.
Repeat the layering of cookies and cream 4 times for a total of 5 layers each of cookies and cream. You will finish with a layer of cream and the pan will be very full. If you use a 9 in springform pan, you may only have 4 layers of each instead of 5.
Cover the pan with plastic wrap and refrigerate overnight.
Before serving, run a knife around the edge of the pan before removing the sides of the springform pan.
Decorate with chocolate shavings if desired and serve cold.