Kefir sauce
Mix kefir, sugar and wine in a small pan and heat to 50 °C, whisking to an emulsion.

For the crumble
Mix the butter, sugar and flour together by hand, working together like a shortcrust pastry, then leave to rest in the fridge for around half an hour, then crumble and bake in the oven at 160 °C for around 14 minutes.

Millefeuille
Make a direct caramel with the sugar and glucose, then as soon as the mixture is
dark amber in colour, halt the cooking by adding the butter.
Mixed together thoroughly, then pour onto a baking sheet with a silpat mat and leave to crystallise.
Once crystallised, blitz in a blender.
Peel the apples and use a slicer to obtain 2 cm thick slices.
On greaseproof paper, build up alternate layers of caramel and apples to a height of approximately 4 cm.
Bake in the oven at 190 °C for 35 min, then remove from the oven and place a baking sheet on top, pressing down, and return to the oven for 10 minutes.
Leave to cool, then cut into portions the following day and lay on top of the crumble.

Zabaglione
Whisk the three ingredients together, egg yolk, sugar and wine, cooking them over a bain-marie until the temperature reaches 83 degrees, then add the cream and the previously soaked leaf gelatin, leave to cool to around 15 degrees, then pour into a whipping siphon and charge with 2 cartridges of N2O.
Leave the siphon to rest in the fridge for around 3 hours before using it.