Dredge lamb cubes in flour on a plate until completely covered.
Brown the lamb in batches with vegetable oil in a casserole over medium heat for 8 minutes.
Remove browned lamb with a slotted spoon and set aside on a plate.
Fry chopped onions and garlic in the remaining oil for 5 minutes until golden.
Add wine and simmer for 8 minutes until volume reduces by half.
Stir in tomatoes and herbs and simmer for 5 minutes until reduced by half again.
Return lamb to the pot and add stock until the meat is covered.
Cover and simmer gently for 90 minutes until the sauce thickens and lamb is tender.
Boil the seasonal vegetables in salted water for 3 minutes then drain.
Sauté the vegetables in butter for 2 minutes until tender.
Serve the lamb over mashed potatoes topped with the buttery vegetables.