In a large bowl, cream together margarine and 1 cup sugar until smooth. Beat in the egg then stir in the cream and vanilla. Combine flour, baking powder, bicarb soda and salt; stir into the creamed mixture. Cover and refrigerate dough for 2 hours or until firm.
To make the filling: In a medium saucepan over medium heat, stir together sugar and flour. Stir in the raisins, walnuts and water. Simmer until thickened while stirring constantly. Remove from heat and allow to cool.
Preheat oven to 180 degrees C. Grease baking trays. On a floured surface roll out dough to 5mm thickness. Using a round cutter, cut out 48 circles about 7cm in diameter. Assemble the biscuits: place one onto the baking tray, place a teaspoon of filling in the centre then cover with another biscuit. Press the edges together with a fork to seal. Repeat with remaining dough, spacing biscuits 5cm apart.
Bake for 12 to 15 minutes in the preheated oven, or until edges are golden brown. Remove from baking trays to cool on wire racks. Caution - filling is hot!