Preparation Steps

• Preheat oven to 325°F (163°C). Line a 9x9 inch square baking pan with aluminum foil or parchment paper, leaving an overhang on the sides to easily lift the bars out later.
• Mix the graham cracker crumbs and melted butter together in a medium bowl. Press the mixture firmly into the prepared baking pan. Bake for 10 minutes, then remove from the oven and set aside to cool.
• In a large bowl, beat together cream cheese, sugar, flour, and vanilla extract with a handheld mixer until smooth and creamy. Add the eggs one at a time, mixing on low speed after each just until combined. Mix in the sour cream until smooth.
• Divide the batter evenly between two medium bowls. Stir in the melted chocolate into one bowl until combined.
• Spread the plain batter evenly on top of the crust. Drop spoonfuls of the chocolate batter on top. Using a knife or a toothpick, gently swirl the two together.
• Bake for 25-30 minutes, or until the cheesecake has set around the edges and only slightly jiggles in the center.
• Remove from the oven. Allow to cool completely in the pan on a wire rack. Then refrigerate for at least 3 hours until very firm.