Pastry: Preheat oven to 200 degrees C. Line a springform tin (26cm in diameter) with baking paper.
Knead the flour with butter, sugar and the egg into a pastry. Roll the pastry on a lightly floured work surface and line the springform pan with it. Cover with baking paper and dried beans.
Bake in the preheated oven on the bottom shelf for approximately 10 minutes. Remove the beans and baking paper then cook for a further 10 minutes.
Filling: Wash the limes with hot water, rub dry and strip the peel with a zest grater into long strips and set aside. Squeeze the limes.
In a saucepan add the lime juice, half the orange juice, butter and sugar then bring to the boil. Reduce heat. Mix the remaining orange juice with the cornflour until smooth and thicken the juice blend with it.
Mix the egg yolks with a little cream. Under constant stirring mix with the rest of the cream. Pour immediately over the cooked pastry base and leave to cool.
Stir the mascarpone in a bowl until smooth. Beat the cream with icing sugar and vanilla sugar until stiff then fold into the mascarpone. Spread over the cooled cream.
Decorate the tart with lime stripes. Cool for at least two hours in the refrigerator.