Put flour, salt, oregano and a pinch of pepper in a bowl. Add cold butter cut into small pieces and knead the ingredients with the fingers for a few minutes to get a sandy mixture. Add grated Parmesan cheese and egg and knead again until smooth and homogeneous. Form a loaf, cover with cling film and allow to rest in the fridge for 30 minutes. In the meantime, prepare the mousse: Stir gorgonzola until creamy in a bowl, add mascarpone and mix.

Take the short pastry out of the fridge. Roll out to 4-5 mm thick on a lightly floured work surface and cut out circles with a cookie cutter with a diameter of 8-10 cm. Cover previously buttered and floured tartlet molds with the circles and prick the tartlet bases with a fork. Put the tartlets on a baking tray and bake in the preheated oven at 180°C (top/bottom heat) for 20 minutes.

Remove from the oven and allow to cool before taking them out of the molds. Put them on a serving tray, fill with gorgonzola mousse and garnish with apple slices.