Pour the flour into a large bowl, add the xylitol and a pinch of salt, then mix well.
Add the butter and rub it thoroughly into the flour mixture until crumbly.
Add the 4 egg yolks and the sour cream. Knead everything together well, then divide the dough into two equal balls. Place them in the refrigerator while you prepare the apples.
Peel and grate the apples, then pour the lemon juice over them. Let them sit for 5 minutes, then squeeze out the juice with your hands and place the drained apples into another bowl. (Save the juice – it’s great as a smoothie base or you can drink it on its own.)
Add the erythritol and cinnamon to the drained apples. Mix thoroughly and set aside.
Butter a 25 cm pie dish.
Remove the dough balls from the refrigerator. On a floured surface, roll out one ball to about 0.5 cm thick. Place it into the pie dish and gently press it into the edges. Feel free to patch any missing spots with your fingers.
Prick the bottom of the dough a few times with a fork. Spread the apricot jam over the crust and sprinkle with the ground walnuts. Add the squeezed apple filling on top, then sprinkle lightly with a little flour.
Roll out the second dough ball to the same 0.5 cm thickness. You can decorate it however you like. I used a cookie stamp for this recipe, but you can also make a lattice top or cut out stars for decoration. Place the dough over the apple filling.
Brush the top with beaten egg and bake in a preheated oven at 190°C / 374°F (top and bottom heat) for 40 minutes.
Once baked, allow the pie to cool completely before slicing.