To do this, mix all the dry ingredients except the butter, pour in the melted butter drop by drop, stir gently with a fork so that lumps form, then chill.
Dough:
Mix the fat, sugar, vanilla sugar and egg until frothy, until the sugar is dissolved. Mix and stir in the flour, baking powder and nuts. Spread the dough in a greased springform pan (bottom lined with baking paper).
Filling:
Peel the apples, cut into cubes, mix in the drained mandarins.
In a mixing bowl, beat the egg and sugar until foamy and carefully add to the fruit. Spread on the dough.
Spread the crumble on the fruit mixture.
Bake at 180 ° C in the middle rack for 50-70 minutes.