Preheat oven to 350 degrees F/ 325 degrees F convection.  Oil an 8 or 9 inch round or square cake pan.

Make the cake.  In a large bowl, beat together oil and sugar until fully combined.  Beat in the eggs one at a time, followed by the vanilla.  Stir in half the flour, followed by the milk.  Finish the batter by stirring in the remaining flour, ginger, baking powder and soda, and salt.  Pour into the prepared pan and smooth into an even layer.  Sprinkle with an even layer of blackberries.

Make the topping.  In a medium bowl, stir together sugar, flour, cinnamon, and ginger.  Stir in the oil and syrup until clumps form.  Sprinkle over top of the blackberries.  Bake for 50-60 minutes until golden brown and a toothpick inserted in the center comes out clean or with a few crumbs.  Cool completely in the pan before serving.  Cake may be stored in an airtight container at room temperature for up to 4 days or frozen, wrapped in parchment and foil and placed in a zipper bag, for up to 3 months.  Thaw in the microwave about 1 minute.