The trick with any frozen meat is to let it thaw so it comes to room temperature. When all parts of the lamb are at around the same temperature, it cooks evenly too. Leave it on the kitchen counter for a maximum of two hours. Else, you can also thaw it in the fridge (not the freezer) section of your refrigerator overnight. Make sure you pat dry the pieces very well. Tip - While thawing the meat, I keep it in a colander and place it in a bowl to collect the liquid.