To make the pastry, whisk the butter and sugar, add the lemon zest, salt and egg and mix well. Add the sifted flour and work quickly. Wrap in cling film and refrigerate for 20 minutes.
Butter and flour 4 tartlet cases. Roll out the pastry and blind bake the four tartlets at 180C for 5-7 minutes.
Place all the ingredients for the lemon filling in a deep base pan and heat gently. Stir continuously until mixture thickens like custard. Pour into the tartlet cases and chill until needed.
To make the balsamic glaze, put the balsamic vinegar, Demerara sugar, star anise and cloves in a pan and cook gently until reduced to one third the original volume. Strain and serve with the strawberries.
Whisk the mascarpone, icing sugar and grated tonka beans until light and fluffy and refrigerate before serving.