I remember the most tender lamb cooked by an elderly Greek gentleman who told me that he had fired up a classic wood–fired oven and made it really hot. He removed all the embers, placed the lamb inside on a tray and after closing the oven, he sealed the door with clay and left the lamb there for many hours, probably up to 8 hours. If you have a wood-fired oven, follow this procedure or simply place the lamb on the cooler side of the oven and leave it there for as long as it takes to get really tender. Alternatively, if you are using a domestic stove set it on 110 degrees celcius and leave it there on a baking rack uncovered for several hours, depending on the size of the joint. I recommend shoulder on the bone. I find that the fat melts away and the meat remains moist.