1. Peel the potatoes and cut them into slices. Immerse them in a saucepan of boiling water with the stock cube added and cook for 15/20 min.
2. Preheat the oven to 215 ° C. Peel the onions and brown them in a pan in olive oil. Add the minced meat, salt, and pepper and cook for about 5 minutes.
3. Roll out a puff pastry in a pie pan and prick the bottom with a fork. Garnish this pie shell with the potatoes and then the minced meat.
4. Fold the puff pastry inwards by about 1 cm. Beat the egg yolk in a bowl with a fork and brush over the folded edge with a brush. Cover the whole with the other puff pastry, taking care to border the turn towards the inside of the mold. Brown the whole with the rest of the egg. Make a small hole in the center of the pie using a knife.
5. Bake for 45 minutes at 200 ° C.