01 - Preheat oven to 325°F (160°C). Grease and line the bottom of a 9-inch (23 cm) springform pan with parchment paper.
02 - Combine crushed chocolate sandwich cookies and melted butter in a bowl until thoroughly moistened. Press mixture firmly into the base of the prepared pan in an even layer. Freeze while preparing remaining components.
03 - Beat softened butter, brown sugar, and granulated sugar using an electric mixer until pale and fluffy. Add milk and vanilla extract; mix to incorporate. Blend in heat-treated flour and salt until combined. Fold in mini chocolate chips. Roll most of the dough into marble-sized balls, reserving some for garnish. Chill until needed.
04 - Beat cream cheese and sugar together until smooth and creamy. Add eggs one at a time, mixing well after each addition. Blend in sour cream, vanilla extract, and flour until just fully combined without overmixing.
05 - Pour half of the cheesecake batter onto the chilled crust. Evenly scatter half of the cookie dough balls over the batter. Add remaining cheesecake batter, gently smoothing the surface. Distribute remaining cookie dough balls on top if desired.
06 - Bake for 55–65 minutes, or until edges are set and the center just slightly jiggles when shaken. Turn off oven, crack door, and allow cheesecake to cool inside oven for 1 hour.
07 - Remove cheesecake from oven and cool completely at room temperature. Cover and refrigerate for at least 4 hours or preferably overnight to set.
08 - Before serving, garnish with mini chocolate chips and extra cookie dough balls. Slice with a sharp, clean knife and serve chilled.