Preheat your oven to 160 C / 325 F. Butter a 9 x 4 inch loaf tin and dust with flour.
To make the filling , beat all ingredients until smooth . Fold in the chopped chocolate
In a large bowl, whisk together the flour , sugar , cocoa , baking soda and salt .
Add the water , oil , vanilla and vinegar and mix until just smooth.
Pour the chocolate batter into prepared pan.
Pour the cheesecake filling down the centre, keeping away from the sides. You can swirl if you wish.
Bake for 40-45 minutes until a toothpick inserted comes out clean.
Cool completely on a rack.
Slice and serve.