Place the condensed milk cans unopened in a high pot. Add enough water to cover the cans. Cover and boil for about 2 hours. (Attention! The cans must be covered with water the whole time.) Then take out of the water (hot!) and boil for at least two hours.
Leave to cool for 45 minutes.
For the shortbread base, grease a tart mould with a removable base (28 cm Ø) and dust with flour. Mix flour, butter in pieces, 1 pinch of salt, sugar and 1-2 tbsp. ice-cold water first with the dough hooks of the mixer, then quickly knead with your hands to a smooth dough.
Roll out round (approx. 32 cm Ø) between two layers of baking paper. Remove the upper baking parchment. Pour the dough into the tin and press down at the edge. Prick the base several times with a fork. Cover and refrigerate in the fridge for about 1 1/2 hours.
Preheat oven (electric cooker: 175°C/circulating air: 150°C/gas: level 2). Open condensed milk cans carefully. Mix caramelised condensed milk and eggs. Sift the starch on top and stir in well. Pre-bake the tart base in the oven for 10 minutes.
Meanwhile, peel, quarter, core and dice the apples and fold them into the caramel cream. Sprinkle the tart base with breadcrumbs and spread the caramel cream on top. Bake at the same temperature on the lowest rack for 35-40 minutes.
Let the tarte cool down.
Just before serving, decorate the tarte with crème fraîche and apple slices.