How to cook
First, make the filling. Put the lamb offal to boil. While it's boiling you can prepare the rest of the meat.
Wash the upper part of the lamb and salt it well on the inside so that the meat can absorb the salt during cooking. Prepare a thick needle with thick thread.
Once the offal has boiled, take it out to cool, so you can cut it into pieces.
Leave to saute well with the lid closed. Once the spinach shrinks in volume, add the rice and stir well, then remove from stove.
Fill the lamb half and sew it closed. Put it in a tray with water. Be sure to put it on wooden sticks to prevent the meat from sticking to the tray. Salt on top and cover with foil so that it can smother well.
Cook in the oven at 374°F (190 °C) for 4-6 hours. Check with a fork after 3-4 hours to see if it's ready and turn the meat over with it. If it's not ready, cover with the foil once again.
Once it is ready, flip it over and add the peeled and chopped potatoes to the tray. If needed, pour in more water.
Leave it without foil to get a nice crisp. Once the potatoes are ready as well, take out and serve.