01 - Preheat the oven to 350°F. Grease a 9-inch springform pan and line the bottom with parchment paper.
02 - Combine crushed chocolate biscuits, melted butter, and sugar in a bowl. Press evenly into the bottom of the pan. Bake for 10 minutes, then let cool.
03 - In a small saucepan, combine strawberries, sugar, and lemon juice. Cook over medium heat until berries soften (about 5 minutes). Stir in cornstarch slurry and cook until thickened, 1-2 minutes. Puree until smooth and let cool.
04 - Beat cream cheese and sugar until smooth. Add eggs, one at a time, mixing well after each. Blend in sour cream and vanilla.
05 - Divide the filling in half. To one half, fold in the melted dark chocolate.
06 - Pour the chocolate filling over the crust, spreading evenly. Top with the plain filling.
07 - Drop spoonfuls of the strawberry puree on top and use a skewer or knife to swirl it through the batter.
08 - Place the pan on a baking sheet. Bake for 50-60 minutes, or until the center is just set and slightly wobbly.
09 - Turn off the oven, leave the door slightly open, and let the cheesecake cool for 1 hour.
10 - Refrigerate for at least 4 hours or overnight before serving.