Oil the bases and sides of two 20cm loose-bottomed sandwich tins using ½ tsp of the oil, then line the bases with baking paper. Put the almond milk in a jug, add the vinegar and leave to sit. Sift the dry ingredients into a large bowl. Make a well in the centre and add the puréed dates, almond milk, oil and vanilla. Beat well until smooth. Divide the mixture between the prepared tins and bake for 25-30 minutes or until a skewer inserted into the middle of the cakes comes out cleanly. Leave to cool in the tins for 10 minutes, then turn out onto wire racks to cool completely.