01 - Preheat oven to 325°F (160°C). Grease and line the bottom of a 9-inch springform pan.
02 - Mix crushed chocolate sandwich cookies and melted butter in a bowl until well blended. Press firmly into the bottom of prepared pan and freeze while making other layers.
03 - In a mixing bowl, beat together the softened butter, brown sugar, and granulated sugar until pale and fluffy. Add milk and vanilla, then blend until combined. Mix in heat-treated flour and salt just until incorporated. Fold in mini chocolate chips. Roll most of the dough into marble-sized balls, reserving some for topping. Chill cookie dough balls in the refrigerator until needed.
04 - Using an electric mixer, beat the cream cheese and granulated sugar until smooth. Add eggs one at a time, mixing thoroughly after each addition. Blend in sour cream, vanilla, and flour only until combined, avoiding overmixing.
05 - Pour half of the cheesecake batter over the chilled cookie crust. Evenly distribute half of the cookie dough balls over the batter. Pour the remaining cheesecake batter over the top and smooth the surface. Arrange reserved cookie dough balls on top if desired.
06 - Bake for 55 to 65 minutes, or until the edges are set and the center is just slightly wobbly. Switch off the oven, crack the door, and allow cheesecake to cool inside for 1 hour.
07 - Remove cheesecake from oven, cool completely at room temperature, then refrigerate for a minimum of 4 hours or overnight.
08 - Before serving, garnish with mini chocolate chips and extra cookie dough balls if desired. Slice and serve chilled.