01 - Preheat oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - Combine graham cracker crumbs, melted butter, sugar, and salt in a medium bowl. Press evenly into the bottom of the prepared pan. Bake for 10 minutes, then let cool slightly.
03 - Beat cream cheese and sugar in a large bowl until smooth and creamy. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract and sour cream.
04 - Spread the cheesecake mixture evenly over the cooled crust.
05 - Mix diced strawberries, strawberry jam, and lemon juice in a small bowl. Dot spoonfuls over the cheesecake layer and gently swirl with a toothpick or knife to create a marbled effect.
06 - Bake for 35 to 40 minutes until the center is just set. Cool to room temperature, then refrigerate for at least 4 hours until firm.
07 - Melt chocolate chips and butter together in a microwave-safe bowl in 20-second bursts, stirring until smooth. Let cool slightly, then spread over the chilled cheesecake bars.
08 - Once the chocolate is set, lift the bars out using the parchment overhang. Garnish with halved fresh strawberries, slice into 12 bars, and serve.