In a food processor, sand dry ingredients and butter butter first. Add the yolk, milk and vanilla and mix to combine. Wrap up and chill completely. Grease tart pan with softened butter. Flour work surface and work out dough to soften – the dough should remain cool and supple. Roll out shortcrust into a 3 mm thick disk. Lay over the tart pan and shape into tart shell.
Blend all ingredients together and keep refrigerated until ready to use.
Peel, core and cut apples into cubes. Sauté apples with butter, sugar and vanilla until most of the moisture is gone and begins to caramelize. Add alcohol and flambé. Transfer apple mixture to a plate to cool off.
Fill the tart shell with the room temperature apple mixture. Cover with the filling two-third up and bake.
Beat egg whites with sugar and add melted butter. Set aside.
Bake at 350ºF/180ºC for 30 minutes. Remove tart from the oven, pour over tart glaze and bake for an additional 10 minutes at 425ºF/220ºC. Serve at room temp – Enjoy!