Heat 1 tablespoon of the olive oil in a flameproof casserole over medium-high heat. In 2-3 batches, brown the diced lamb all over for 3-4 minutes, then remove and set aside.
Add the remaining 1 tablespoon of olive oil and the onion, then cook, stirring, for 2-3 minutes until the onion begins to soften. Add the chilli, garlic and chopped rosemary, then cook, stirring, for 1-2 minutes until fragrant.
Return the browned lamb to the casserole, then add the white wine and simmer for 2-3 minutes. Stir in the tomato passata and bay leaves, season with sea salt and freshly ground black pepper, then bring to a simmer over medium heat. Stir in the olives, then cover and cook in the oven for 1 hour 30 minutes or until the lamb is tender and the sauce has thickened.
Lay the feta wedges on a plate and sprinkle with the crushed mixed peppercorns and half the chopped mint.
Divide the lamb casserole among bowls, then scatter with the remaining mint. Serve the casserole with the peppered feta to crumble over, and crusty bread to mop up the sauce.
Passata is sieved tomatoes, available from supermarkets and delis.
This recipe can be made ahead and reheated, the flavour just gets better, but dont put the fetta on until you are ready to serve