Cover the casserole/dish (if your dish doesn’t have a lid, use aluminium foil and stretch it to the edges of the dish in order to minimise evaporation and the loss of juices) and place it on the lowest rack of the oven. Adjust the heat so that the liquid simmers very slowly, it has to go on for 3-4 hours. I cooked it at 150ºC – 300ºF for 3 and a half hours.