Grease a 28 x 18 cm (11 x 7 inch) deep Swiss roll tin lightly with butter and line the base with nonstick baking paper.
Place 150 g (5 oz) of the butter into a bowl and beat well until smooth with a wooden spoon. Add the sugar, 150 g (5 oz) of the soft cheese and the vanilla essence and beat again. Add the eggs and sift in the flours. Mix together to combine well.
Fold the blueberries into the cake mixture, then transfer to the prepared tin and level. Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20 minutes until golden and firm to the touch. Allow to cool for 10 minutes in the tin before turning the cake out on to a wire rack to cool completely.
Beat together the remaining soft cheese and remaining butter with the icing sugar and half of the cinnamon, if using, and spread over the surface of the cake. Cut into 12 squares, then sprinkle with the remaining cinnamon, if liked.