There will be plenty of jam left over from this recipe, so spoon
it into sterilised jars, seal and bring them to a simmer in a
saucepan of water for 10 minutes, then, once cool, store them in
For blood plum conserva, combine plums in a large saucepan with lemon juice and 125ml water. Bring to the boil, stirring occasionally, until plums start to break down (4-5 minutes). Add sugar, stir to dissolve, then boil mixture vigorously until setting point has been reached (8-10 minutes). Cool, and refrigerate until required.
Beat butter, icing sugar and a pinch of salt in an electric mixer until pale and fluffy (2-3 minutes), then stir in flour and gently knead until a soft dough forms. Wrap in plastic wrap and refrigerate until firm (1 hour).
For buttercream, beat butter and fondant in an electric mixer until pale and creamy (3-4 minutes).
Preheat oven to 170C. On a lightly floured work surface roll out pastry to 5mm thick, then, with a 6cm fluted biscuit cutter, cut out 24 rounds and place them on oven trays lined with baking paper. Scatter raw sugar over biscuits and bake until light golden (8-10 minutes), then cool on wire racks.
To assemble, spread the bases of half the biscuits with 1 tbsp of blood plum conserva and the remaining biscuits with buttercream, then sandwich together. Biscuits will keep unfilled in an airtight container for 5 days. Filled biscuits are best eaten within an hour of filling.