Line a 30cm x 20cm baking tray with baking parchment. Preheat the oven to 220C/fan 200C.
In a small bowl, add the vinegar to the soya milk and give them a stir (this will make the soya milk curdle and thicken); set aside.
Sift the flour into a large mixing bowl and then add the sugar, baking powder, oil and vanilla essence. Pour in the curdled soya milk/vinegar mixture and stir to mix thoroughly.
Fold in the frozen raspberries. Pour the mixture into the baking tin and bake until firm and springy to touch and a toothpick inserted into the middle comes out clean (about 20-25 min).
When the cake is done, take hold of the edges of the baking parchment and lift the cake out of the tin and on to a cooling rack, baking parchment and all, and leave to cool.
Once the cake has cooled, pour a little boiling water onto a few raspberries and press with the back of a spoon to extract a pinkish raspberry-flavoured liquor. Half fill a teacup or small bowl with icing sugar and start to add the pink liquid a little at a time, stirring continually, and adding more icing sugar if necessary, until you have thick pouring consistency. Drizzle the pink icing backwards and forwards across the cake in whatever pattern takes your fancy and cut into slices to serve.