Preheat oven to 180°C. Grease a 20cm round baking tin and line with baking paper.
Beat the butter, caster sugar and icing sugar together with an electric mixer until light and creamy. Add the eggs, one at a time as well as the vanilla and jam. Beat until combined.
In a separate bowl, combine the sifted flour, bicarb and cocoa. Fold into the mixture alternately with the milk. Stir until just combined and almost smooth.
Pour into prepared tin and bake for approximately 45 minutes or until cooked through. Leave it to cool in the tin for 15 minutes before turning out onto a wire rack to cool completely. Top with icing.