Heat 1 tablespoon olive oil in a large casserole pot and brown the lamb pieces, ideally in batches, making sure the first lot is brown before moving on and browning the next amount. Lift each batch out of the pan and set to one side until all of it has browned. Keep the browned lamb covered with a plate. 

Add a second tablespoon of oil to the pan add the onions, scraping the bottom of the pan where the lamb has been browning. 

Cook the onions very gently for 10 minutes until softened. Add a few tablespoons of water to help the onions along and keep the pan from drying out. 

Add the garlic and tomato puree, stir and cook for a further five minutes.

Tip the browned lamb back in, add the tin of tomatoes and then half fill the can with water and tip that in. Add the cinnamon and dried or fresh oregano. Cook on a low, gentle heat for ten minutes, stirring occasionally. Bread up the tomatoes with a spoon if they were whole and not chopped. 

Stir the orzo into the casserole pan, stir well and pour over the stock. Cook, uncovered, for a further 10-11min or until the orzo is tender. It should not be too soft, but rather al dente. Season with lots of salt and pepper.

Once cooked, carefully spoon onto a large serving dish, sprinkle over the fresh mint and the crumbled feta. Serve immediately.