Meanwhile in a small pot heat up chopped apple, sugar, water and vanilla paste. Once it starts bubbling, take it down to a low heat and let it simmer under a lid for 8 min.
Then take the pot off the heat and sieve the juice from the apples over a bowl. Squeeze the excess water off the gelatine and stir it in into the apple purée until smooth. Let it cool down on the counter until it reaches a temperature between 29-30ºC.
Once cooled down, gently stir in the skyr, with a spatula, into the apple purée in three parts.
Whip the with heavy cream until soft peaks. With the rubber spatula, gently fold together the whipped cream in 3 parts with the apple purée. Once smooth and combined, pour it into a 16 cm silicone mold.
Place it in the freezer for a minimum of 4 hours or overnight.
APPLE FRANGIPANE
TART DOUGH
In a food processor, blend flour, almond flour, powdered sugar, cinnamon, nutmeg and the cold butter together until the butter is blended with the dry ingredients.
Then add the egg and blend it until it has just gathered.
Transfer the dough to a piece of plastic film and let it rest in the refrigerator for a minimum of 2 hours or overnight.
Turn on the oven at 180ºC.
Dust a silicone mat or piece of baking paper with a bit of powdered sugar, as well as the rolling pin. Roll out the dough until the dough has a thickness of 2 mm. Freeze it for 20 min.
Cut the dough so it fits the tart mold and place the dough in the mold. Set it aside while you prepare the filling.
FRANGIPANE FILLING
Whisk all the ingredients in a bowl until light and fluffy. Pour in ⅔ of the filling into the tart pan and even it out. Cut some thin slices of apple and place it in a circle on the frangipane.
Bake for 20-25 min, until golden brown.
Let it cool down completely.
ASSEMBLING
Place the apple mousse on top of the frangipane tart and let it defrost in the fridge for a few hours. When ready to serve, decorate with thin apple slices and crystalized whites chocolate.