Preheat the oven to 300°F / 160°C and grease a 9" springform pan with butter.
Make the crust: Put the cookies and sugar in the food processor, and pulse until crumbs (reserve 2 tablespoon for topping).
Add the melted butter and beat again until the mixture resembles wet sand.
Press the mixture into the bottom and sides of the springform pan.
Bake in the oven for 15 minutes. Remove from the oven, and let it cool.
Make the filling: In a microwave-safe bowl, add milk and chopped chocolate and microwave for 20 seconds or until the chocolate melts.
In a mixing bowl, whisk together the cream cheese and sugar until combined.
Mix in the eggs one at a time, along with the vanilla extract. Then, stir in the flour and the chocolate mixture until well combined.
Assemble the chocolate cheesecake: Carefully pour the filling over the crust in the springform pan and bake for an hour.
Cool it gradually: Turn off the oven, let the cheesecake cool in the oven with the door slightly open for an hour, then remove it from the oven to cool completely at room temperature.
Chill it: Sprinkle the reserved crumbs on top of the cheesecake, then chill it for at least 6 hours. I chill it overnight.
Notes
Store leftovers in an airtight container in the fridge, and they will last for 3-4 days.