Preheat the oven to 375 degrees and line the bottom of a buttered 8-inch round tin (2 inches deep) with parchment paper. Melt the cane syrup or black treacle. Beat the egg with the buttermilk. Sift together the flour, baking soda, ground ginger, ground cinnamon, brown sugar and a pinch of salt. Mix the dried currants or raisins. Add the egg mixture, then add the syrup mixture and mix well.
Bake for 10 minutes, then turn the heat down to 325 and bake 35 to 40 minutes longer. A few crumbs stick to a tester when the cake is done.