Heat up the oil in a frying pan on medium high flame.
Cook the lamb shank for about 2 minutes per side minimum, more if you want less rare.
Prepare a baking sheet and broil for 4 minutes, flipping halfway. Remove and set aside to cool.
Put the same pan back on medium flame with the onions and garlic and cook for about 5 minutes. Then lower to a simmer and add in all the rest of the ingredients, let cook on low for 45 minutes covered. Pour over the lamb.