Mix the egg with sugar and butter at room temperature. Rub the mixture.

Pour in wheat flour and add sour cream.

Knead the dough until it turns out soft, elastic, and slightly sticks to the hands. Leave it in the refrigerator for 20 minutes.

Roll out the dough into a circle with a diameter of 20-25 cm and 2 cm thick. Spread the dough into a cake pan (tart pan) greased with oil.

From the scraps of dough, cut out stars for topping the tart later.

Bake the base and stars separately for 15 minutes at 200°C or until golden brown.

While the base is cooling, warm up the milk (do not boil) for making mascarpone filling.

In a separate bowl, grind the egg yolks with sugar, add the flour (vanilla sugar if desired) and mix.

Pour the resulting egg mixture into the hot milk and stir.

Simmer for a couple of minutes, stirring constantly, but do not boil! The pastry cream will gradually thicken. Add the butter and mix. Leave the cream to cool.

Fill the buttery pastry crust with the prepared cream filling, and place it in the refrigerator to allow the cream pie filling to harden.

After the cream pie filling has hardened, decorate the tart with fresh berries and Matariki stars to add a pop of color and balance out the richness of the cream.