Fit the dough tool. Place the butter and sugar in the bowl and cream until pale and light.
Add the lemon peel, a few drops of vanilla extract, egg and flour, mix; the dough should be very sticky and soft.
Divide the dough in half. Place each half between two sheets of greaseproof paper, then roll out using quick, light strokes until the dough is approximately 2mm thick. Leave the dough between the sheets of greaseproof paper and slide onto the refrigerated baking tray.Refrigerate for approximately 30 minutes.
Preheat the oven to 160°C.
Slide the dough off the baking tray and onto the work surface. Remove the top sheet of greaseproof paper, cut the dough into rounds with an 8.5cm fluted cutter. Lift the rounds from the greaseproof paper, place onto the buttered baking tray. Bake for 10 minutes or until golden brown. Leave to cool on the baking tray for a few minutes, transfer to a wire rack.
For the Mascarpone Cream:
Still using the dough tool, place all the ingredients in the bowl and beat until smooth and thick. Transfer into a piping bag fitted with a large star-shaped nozzle.
Decorate the centre of the shortbread biscuits with mascarpone cream, arrange the berries around.
Place another shortbread biscuit on top of the cream.