Heat oven to 350F. Grease and line the bases of 6 dariole moulds or individual metal pudding basins with baking parchment or grease-proof-paper. Put the butter, sugar, egg, flour, ground almonds, baking soda, cocoa and milk in a mixing bowl. Beat together until lump-free. Divide between the tins then bake for 20-25 minutes until risen and a skewer poked in comes out clean. Cool for 15 minutes, then remove from tins and cool completely upside down.
Mix the two chocolates in a heatproof bowl. Heat the cream to just below boiling point, then pour over the chocolate and stir together until melted and smooth. chill until think enough to spread.
Use a small dot of icing to stick a marshmallow to the top of each cake. Completely ice all the marshmallow-topped cakes. Dot with chocolate drops to look like the outside of a dalek, add a few small sticks of liquorice or pocky sticks to be the guns, arms and eye-sticks