Preheat the oven to 106°C. Prepare the loaf cases, by putting them into a baking tray. Cream together the butter and sugar until pale, light in colour. Sift the flour, baking powder, and then add this to the creamed butter and sugar mix. Then move on to grate and juice 1 and 1/2 lemons (reserve half the rind of the lemon for decoration) and add to the mixture. Gradually add the beaten eggs, making sure all is combined before adding the next. Divide the mixture between the mini loaf cases equally. Bake in the oven for 25-30 minutes or until golden brown. Leave the cakes to cool before piping. When the cakes are cooled, use a sharp knife to cut a upside-down, cone shape out the top of the cake. Fill the hole in the loaf cake with the Bay Tree's blueberry and lemon marmajam and then place the cut out cake back on top. For the decoration, beat the butter until paler in colour and light in texture. Add vanilla and mix until it is combined. Then add the icing sugar gradually and mix. Add a teaspoon of milk until the icing reaches the perfect consistency. If preferred colour with a part blue, part purple food colour. Pipe onto the cooled cakes using a wilton 2D piping tip. Decorate with fresh blueberries and a thin slice of lemon rind.
