This recipe is intended for the skilled cook only due to some advanced techniques. That said, it is a wonderful recipe and worth the work.
Remove lamb from packaging and butchers netting (if needed). Lay out on a large cutting board. Now you need to lay the shoulder out as flat a possible. Depending on how it was butchered, you may need to make a couple of cuts to open the shoulder up the whole way so you can lay it flat.
Now remove any excess fat and silver skin from both the inside and outside of the shoulder. You can leave a thin layer of fat on the outside of the shoulder if desired.
Now it is time to pound it out with a meat mallet. Cover the roast with a plastic bag or wrap and start pounding. The idea is to make the meat even in thickness all around. Make sure to hit it firm, but not too hard. You don’t want to tear the meat.
Once you are satisfied it is pounded enough, you should be left with something resembling a semi-rectangle. Cut in half making two squares so that you can make 2 small roasts.
Bring the lentils to a boil with 2 cups of water. As soon as its boiling reduce heat to medium high. Add a little salt and coriander to the water for flavour. Boil for about 5 minutes and then remove from the heat. Let sit for another 5 minutes or so and the lentils will absorb any remaining liquid.
Preheat a medium fry pan on medium heat. Add the butter and let it melt a little and then add the mushrooms and the onions. Sauté for about 8 minutes, stirring occasionally.
Once the mushrooms are browned, add the zucchini. Sauté for another 5 minutes.
Add the garlic and sauté for 2 minutes more, stirring frequently.
Season mixture with cumin, salt and pepper to taste.
Add the stuffing to the center of each of the lamb roasts, carefully roll and then tie with butchers twine or string every inch or so to hold everything in place.
Preheat the oven to 325° F and also a large fry pan on medium heat. Season the outside of the roasts with salt and pepper.
Add a little oil to the pan and then the roasts. Brown nicely all around and then transfer to the oven.
Roast for 90 minutes then remove from the oven and let rest for 10 minutes. Slice and serve.
Adding some red pepper or eggplant to the stuffing mix would be nice.
Season the outside of the roast with some ground coriander and paprika for a bit of a notch up in flavour.