In a large dutch oven or heavy-bottomed pot, heat the vegetable oil over medium-high heat. Once hot, add the cubed lamb and sear until nicely colored on all sides. Transfer the seared lamb to a large bowl and set aside. You will need to do this in batches.
In the same pot, reduce the heat to medium and fry the onion and garlic cloves, taking care not to burn them. Once fragrant and starting to color, about 5-8 minutes, add the tomato concentrate, flour and rosemary. The mixture will become dry. Continue to cook, stirring frequently. After a couple of minutes, add the white wine and reduce until there is no liquid left in the pot. Add the stock, olives and peel. Bring the liquid to a simmer and add the meat and any collected juices back into the pot. Stir well.
Leave the lid slightly ajar and continue to simmer for about one hour, or until the meat is tender and comes apart easily. The liquid in the pot will have reduced as well. Pick out and discard the orange peel.
I like to serve this with mashed potatoes as the base. A great way to catch all the delicious sauce.