01 - Preheat oven to 325°F (160°C). Grease a 9-inch springform pan and line the base with parchment paper for easy removal.
02 - Combine crushed chocolate sandwich cookies and melted butter in a bowl. Mix until combined and the texture resembles wet sand. Press mixture firmly and evenly into the bottom of the prepared pan. Transfer to freeze while preparing the next steps.
03 - In a mixing bowl, cream together the softened butter, brown sugar, and granulated sugar on medium speed until light and fluffy. Mix in milk and vanilla extract. Add heat-treated flour and salt, mixing on low speed until just combined. Fold in mini chocolate chips. Form most of the dough into small balls, about the size of marbles, reserving some for the topping. Refrigerate until ready to use.
04 - Using an electric mixer, beat softened cream cheese and granulated sugar until smooth and creamy. Blend in eggs one at a time, beating briefly and scraping the sides after each addition. Add sour cream, vanilla extract, and flour, mixing until just incorporated; do not overbeat.
05 - Pour half of the cheesecake batter over the chilled cookie crust. Distribute half the cookie dough balls over the layer. Pour remaining cheesecake batter evenly over the cookie dough. Gently smooth the surface and top with reserved cookie dough balls, if desired.
06 - Bake in the preheated oven for 55 to 65 minutes, until the edges look set and the center jiggles slightly when gently shaken. Turn the oven off, crack the door open, and let the cheesecake cool in the oven for 1 hour to prevent cracking.
07 - Remove the cheesecake from the oven and let cool completely on a wire rack at room temperature. Once cooled, refrigerate for at least 4 hours or overnight before serving.
08 - Just before serving, sprinkle the top with mini chocolate chips and extra cookie dough balls if desired. Cut into slices and serve chilled.