In a deep bowl, mix the sugar, salt, egg, and flour with a spoon. Pour in the melted, cooled butter.

Knead the dough, gather it into a ball, and chill in the fridge for one hour.

Divide the chilled dough into 3 parts. Roll each into a rectangular sheet no more than 0.5 cm thick, sized to fit your baking tray. Gather the scraps into a ball and set aside - they'll be used for the strips.

Wash the apples, cut in half, remove the cores, and slice thinly. Arrange the slices over the dough rectangles, leaving a 1 cm border; sprinkle with vanilla sugar if you like.

Roll out the reserved dough scraps and cut into strips. Arrange them in a lattice over the apples and brush with beaten egg.

Bake in a preheated 200°C oven for 20 minutes. Cut the cookies into pieces while still hot - and enjoy with tea!