Preheat your oven to 325°F (160°C). In a mixing bowl, stir together the graham cracker crumbs, melted butter, and 2 tablespoons of sugar. Mix until the crumbs are evenly coated. Press the mixture firmly into a parchment-lined 9×13-inch baking dish. Bake for 8 to 10 minutes, then let it cool slightly.
Use an electric mixer to beat the room-temperature cream cheese in a large bowl until smooth. Gradually add the remaining sugar and beat until fully incorporated. Add eggs slowly, mixing well after adding each to ensure a smooth batter. Add vanilla extract and sour cream, mixing until the filling is smooth and creamy.
Melt the chocolate chips in a microwave-safe bowl in 30-second increments until fully melted. Let it cool slightly. Pour the cheesecake filling over the crust. Drop spoonfuls of melted chocolate on top. Use a skewer or toothpick to gently swirl the chocolate into the filling in figure-eight motions.
Place the pan in the oven and bake for 35–40 minutes, checking that the edges are firm while the center remains a bit soft and jiggly. Let the bars cool at room temperature for 30 minutes, then refrigerate for at least 2 hours (preferably overnight) before slicing.
