Preheat oven to 350°F (180°C). Line 20 cm square cake pan with foil, leaving overhang for handles. Set aside.
In heatproof bowl over saucepan of hot (not boiling) water, melt chocolate; let cool slightly. Meanwhile, in separate bowl, beat cream cheese with half of the granulated sugar until smooth. Beat in 1 of the eggs and half of the vanilla; set aside.
In separate bowl, beat butter with remaining granulated sugar until fluffy. Beat in remaining egg. Beat in all but 2 tbsp of the jam and the remaining vanilla, then add the chocolate, mixing well. In small bowl, whisk together flour, baking soda and salt; mix into chocolate batter just until combined.
Spread chocolate batter in prepared pan. Layer with cream cheese mixture. Spoon remaining jam, in small dollops, over top. With a knife, zigzag through cheese and jam layers for marbled effect.
Bake until tester inserted in centre has only a few crumbs clinging, about 40 minutes. Let cool in pan on rack. Cover and refrigerate until chilled, about 2 hours. Remove from pan. Cut into squares, wiping knife between slices. One square is one serving.
Per serving: 2 g protein, 7 g fat (5 g saturated fat), 30 mg cholesterol, 10 g carbohydrates, 1 g fibre, 100 mg sodium.